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Current concepts in biomechanical interventions for patellofemoral pain

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Abstract and Figures

Patellofemoral pain (PFP) has historically been a complex and enigmatic issue. Many of the factors thought to relate to PFP remain after patients' symptoms have resolved making their clinical importance difficult to determine. The tissue homeostasis model proposed by Dye in 2005 can assist with understanding and implementing biomechanical interventions for PFP. Under this model, the goal of interventions for PFP should be to re-establish patellofemoral joint (PFJ) homeostasis through a temporary alteration of load to the offended tissue, followed by incrementally restoring the envelope of function to the baseline level or higher. High levels of PFJ loads, particularly in the presence of an altered PFJ environment, are thought to be a factor in the development of PFP. Clinical interventions often aim to alter the biomechanical patterns that are thought to result in elevated PFJ loads while concurrently increasing the load tolerance capabilities of the tissue through therapeutic exercise. Biomechanics may play a role in PFJ load modification not only when addressing proximal and distal components, but also when considering the involvement of more local factors such as the quadriceps musculature. Biomechanical considerations should consider the entire kinetic chain including the hip and the foot/ankle complex, however the beneficial effects of these interventions may not be the result of long-term biomechanical changes. Biomechanical alterations may be achieved through movement retraining, but the interventions likely need to be task-specific to alter movement patterns. The purpose of this commentary is to describe biomechanical interventions for the athlete with PFP to encourage a safe and complete return to sport. LEVEL OF EVIDENCE:5.
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The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 877
ABSTRACT
Patellofemoral pain (PFP) has historically been a complex and enigmatic issue. Many of the factors thought
to relate to PFP remain after patients’ symptoms have resolved making their clinical importance difficult to
determine. The tissue homeostasis model proposed by Dye in 2005 can assist with understanding and imple-
menting biomechanical interventions for PFP. Under this model, the goal of interventions for PFP should be
to re-establish patellofemoral joint (PFJ) homeostasis through a temporary alteration of load to the offended
tissue, followed by incrementally restoring the envelope of function to the baseline level or higher.
High levels of PFJ loads, particularly in the presence of an altered PFJ environment, are thought to be a factor
in the development of PFP. Clinical interventions often aim to alter the biomechanical patterns that are
thought to result in elevated PFJ loads while concurrently increasing the load tolerance capabilities of the
tissue through therapeutic exercise. Biomechanics may play a role in PFJ load modification not only when
addressing proximal and distal components, but also when considering the involvement of more local factors
such as the quadriceps musculature.
Biomechanical considerations should consider the entire kinetic chain including the hip and the foot/ankle
complex, however the beneficial effects of these interventions may not be the result of long-term biome-
chanical changes. Biomechanical alterations may be achieved through movement retraining, but the inter-
ventions likely need to be task-specific to alter movement patterns. The purpose of this commentary is to
describe biomechanical interventions for the athlete with PFP to encourage a safe and complete return to
sport.
Level of Evidence: 5
Keywords: Foot, hip, knee, rehabilitation, running
IJSPT
CLINICAL COMMENTARY
CURRENT CONCEPTS IN BIOMECHANICAL
INTERVENTIONS FOR PATELLOFEMORAL PAIN
Richard W. Willy, PhD, PT, OCS1
Erik P. Meira, PT, DPT, SCS, CSCS2
1 Department of Physical Therapy, East Carolina University,
Greenville, NC, USA
2 Black Diamond Physical Therapy, Portland, OR, USA
CORRESPONDING AUTHOR
Richard Willy
Assistant Professor
Department of Physical Therapy
College of Allied Health Sciences
East Carolina University
Greenville, NC 27834
Fax: 252-744-6240:
E-mail: willyr@ecu.edu
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 878
BACKGROUND
Patellofemoral pain (PFP) has historically been a
complex and enigmatic issue. Many factors have
been identified to correlate with symptoms includ-
ing variations in strength, flexibility, patellar track-
ing, quadriceps angle, and patellofemoral joint (PFJ)
morphology. There are also known correlations with
psychological factors such as depression, fear-avoid-
ance, and anxiety which complicate the presenta-
tion further.1
Factors thought to relate to PFP often remain after
patients’ symptoms have resolved making their
clinical importance difficult to determine.2 Further
complicating assessment, the pain source in PFP
may involve multiple structures and is highly con-
troversial.2 As such, a thorough clinical assessment
of an individual is paramount to fostering successful
patient outcomes in this population. Although this
commentary will explore biomechanical interven-
tions for PFP, this pathology may be better under-
stood in the context of the tissue homeostasis model.
HOMEOSTASIS MODEL OF
PATELLOFEMORAL PAIN
In 2005, Dr. Scott Dye proposed a tissue homeostasis
model for understanding PFP.2 When any tissue is in
homeostasis, it is maintaining a constant physiologi-
cal condition of its internal environment. Although
very successful at self-regulation, sufficient disrup-
tion of homeostasis can result in pathophysiologic
processes. Instead of considering the presentation of
PFP strictly from a perspective of structural failure,
Dye suggested that the pathophysiologic processes
that occur in response to sudden bouts of increased
training loads or stressors should be seen as the true
driver of symptoms.2
Homeostasis can be described as a zone, or “envelope
of function”, where the tissue is capable of tolerating
loads.2 It has been suggested that this zone is estab-
lished through chronic loads to which the PFJ and
related structures have adapted in response to con-
sistent and incremental exposure.3 Acute increases
in training loads that exceed the established enve-
lope of function are thought to disrupt homeostasis
of the PFJ, ultimately resulting in pain. A central
tenet of the envelope of function is that high PFJ
loads are not inherently dangerous; rather loads that
exceed a tissue’s conditioned capacity may be what
are potentially injurious. Indeed, acute increases
in training load that exceed chronic training loads
appear to play a role in the development of many
sports-related injuries.3,4
Once this homeostasis of the tissue is disrupted
by sudden increases in training loads, the PFJ and
associated structures may no longer tolerate levels
of loading even during routine activities, such as
descending stairs or previously well-tolerated run-
ning distances.2 The goal of intervention at this
point should be to re-establish homeostasis through
a temporary alteration of PFJ loads, followed by
incrementally restoring the envelope of function to
the baseline level or, preferably, higher. The biome-
chanical interventions described in this commentary
can be particularly helpful at temporarily reducing
loads while trying to re-establish homeostasis of the
PFJ.6 Further, an understanding of the biomechanics
of therapeutic interventions for PFP can also assist
the clinician with planning a rehabilitation program
that incrementally restores a patient’s envelope
of function. The purpose of this commentary is to
describe biomechanical interventions for the athlete
with PFP to encourage a safe and complete return
to sport.
BIOMECHANICAL OVERVIEW OF
PATELLOFEMORAL PAIN
High levels of patellofemoral loads, particularly in
the presence of an altered PFJ environment,7 are
thought to be a factor in either the development or
chronicity of PFP.8-10 A PFJ that has relatively low
PFJ contact area11 or diminished cartilage thickness
and properties,7,12 transfers greater loads to the sub-
chondral bone.8 Indeed, individuals with PFP dem-
onstrate increased water content13 and metabolic
activity14 in the subchondral bone of the patella.
Therefore, clinical interventions often aim to alter
the biomechanical patterns that are thought to result
in elevated PFJ loads while concurrently increasing
the load tolerance capabilities of the tissue through
therapeutic exercise.
Interventions that address biomechanical loading of
the PFJ should encompass multiple loading param-
eters. Clinicians should familiarize themselves with
the sport-specific loading demands that their athlete
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 879
mometry during testing, either handheld (isometric)
or isokinetic. Handheld dynamometry is a reliable
measure of quadriceps strength (ICC=0.72)24 with
even greater reliability when straps are used to sta-
bilize the dynamometer (ICC=0.96).25 As clinicians
in non-research settings typically lack access to iso-
kinetic dynamometers, the use of an inexpensive
handheld dynamometer is highly advisable in the
assessment of quadriceps strength in athletes with
PFP.
Progressive quadriceps strengthening is a foundation
of rehabilitation of the athlete with PFP. In high qual-
ity studies, there is consistent evidence that progres-
sive quadriceps strengthening improves symptoms
and function in these patients.26 Progressive quadri-
ceps resistance exercises have been shown to reduce
PFP by 44-90%.26,27 While targeted strengthening
of the vastus medialis oblique (VMO) is often pre-
scribed, there is inconclusive evidence supporting its
superiority to generalized quadriceps strengthening
for the treatment of individuals with PFP. 26,28 There-
fore, the authors of this commentary have considered
the literature on generalized quadriceps strengthen-
ing and VMO-targeted strengthening together.
The results of a quadriceps strengthening program
may be enhanced through the use of patellar tap-
ing or bracing. The effect of patellar taping on PFJ
kinematics and PFP remains somewhat controver-
sial. Although the application of patellar tape results
in large and immediate reductions in pain,29 pain
reductions occur with either directionally applied
or non-directionally applied tape.30 These findings
are suggestive of a non-biomechanical mechanism
for the reduction in pain that is often observed with
patellar taping. Patellar taping may enhance the
ability to perform quadriceps resistance exercises in
individuals with PFP,31 presumably by reducing pain-
related quadriceps inhibition. Thus, patellar taping
may enable greater PFJ loading during quadriceps
resistance exercises that would ordinarily result in
pain.29 In support of this rationale, recent system-
atic reviews indicate that patellar taping enhances
patient outcomes, but only in the first 12 weeks of
rehabilitation6,32 when pain would be expected to be
the greatest. Patellar bracing may also have a simi-
lar influence on outcomes in individuals with PFP
through the 6 and 12 week time points.33 As such,
with PFP may experience. Running, for instance, is
a highly repetitive activity in which relatively high
loads of 4-5.5 times body weight15-17 are applied to
the PFJ at a moderately high rate18 (Figure 1). Thus,
a rehabilitation program for the running athlete
with PFP should include components that expose
the extensor mechanism to high loads at a relatively
moderate rate, with an emphasis on repetition. In
contrast to running, the jumping athlete likely expe-
riences PFJ reaction forces well in excess of 10 times
body weight19 applied at a much higher rate, but with
fewer repetitions. A well-planned rehabilitation pro-
gram for any athlete with PFP should reflect these
sport-specific demands to ensure a durable return
to sport.
CONSIDERING THE QUADRICEPS
Quadriceps weakness is an established risk factor for
the development of PFP20 across a variety of popu-
lations. Quadriceps weakness may be indicative of
inadequate chronic training loads and, ultimately, a
PFJ that has a relatively low envelope of function.
Individuals who develop PFP have been found to
have quadriceps strength deficits of 6-12% compared
with healthy control participants20-23 which are unde-
tectable via manual muscle testing. As such, out-
come measures documenting quadriceps strength
in this population should utilize some form of dyna-
Figure 1. The patellofemoral joint and related structures expe-
rience three aspects of loading a) the peak load per step, b) how
quickly this load is applied (rate of loading and 3) the total accu-
mulation of load during an activity. These metrics are impor-
tant to consider in the development of rehabilitation programs
for individuals with patellofemoral pain.
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 880
exercises. Specifically, clinicians should consider
carefully the interactions between external moment
arms, external and internal loads, knee joint angles
and articular contact area of the PFJ when prescrib-
ing quadriceps strengthening exercises. In either
open or closed kinetic chain, contact area of the PFJ
is the lowest in the first 20 degrees of knee flexion
and steadily increases as knee flexion increases.11,40
Interestingly, the external moment arm acting
on the knee also increases as an individual moves
deeper into a closed kinetic chain squat. As a result,
PFJ stress (the quotient of PFJ reaction force and
PFJ contact area) increases fairly linearly from full
knee extension to approximately 45 degrees of knee
flexion during a squatting maneuver.41,42 However,
PFJ reaction forces increase rapidly from approxi-
mately 45 degrees to 100 degrees of knee flexion with
either a squat or leg press43 with a disproportionate
lower rate of increase in PFJ contact area.40 The net
result is that PFJ stress is considerably higher when
squatting and leg presses in knee flexion angles in
excess of approximately 45 degrees when compared
with squatting with comparatively less knee flexion
(Figure 2 and 3A).41 Thus in the early stages of reha-
bilitation of PFP, the PFJ is particularly well-suited
to closed chain loads, in approximately the first 45
degrees of knee flexion.41
Quadriceps strengthening can also be achieved with
open kinetic chain exercises. However, PFJ loads
during open chain exercises are highly dependent
on the configuration of force application. During
open chain knee extension with a weight attached
to the ankle, the external moment arm increases as
the knee nears full extension. This loading configu-
ration results in a highly variable level of external
resistance throughout the knee extension motion
(EXT-VR) as shown in Figures 2 and 3B. Thus, PFJ
reaction forces increase rapidly as the knee nears
full extension in the open chain43 whereas PFJ con-
tact area decreases precipitously. This loading sce-
nario results in a large increase in PFJ stress in the
last 20 degrees of knee extension, which is exactly
opposite of what occurs during a squatting maneu-
ver.41 In contrast, a knee extension machine that
uses a cable system applies external resistance in a
fairly uniform manner throughout the knee range of
motion, via a constant external moment arm (EXT-
CR) as shown in Figure 2 and 3C.41,44 Knee exten-
it appears that recovery from PFP may be bolstered
by the addition of patellar taping or patellar bracing,
but only in the first 6-12 weeks of a patellofemoral
rehabilitation program.
THE QUADRICEPS STRENGTHENING
PARADOX
Despite the consistent improvements in pain asso-
ciated with quadriceps strengthening, the mecha-
nism behind reported pain reductions is unclear. For
instance, quadriceps strengthening exercises may
potentially expose the PFJ to high reaction forces
which are thought to exacerbate PFP. Conversely,
it has been proposed that quadriceps strengthening
may alter patellar kinematics, potentially increasing
the contact area between the patellar and trochlear
articular surfaces. To date, preliminary evidence
suggests that eight weeks of quadriceps strengthen-
ing may result in increased contact area of the PFJ.34
Thus, quadriceps strengthening may reduce PFJ
stress by increasing the contact area of the PFJ.
Ultimately, the process of quadriceps strengthening,
rather than the quadriceps strength gains that result,
may reduce PFP by improving load tolerance of the
patient and the PFJ structures. For instance, quadri-
ceps strengthening results in a desirable increase in
glucosaminoglycan content in articular cartilage of
the knee.35 In an animal model, eccentric quadriceps
muscle contractions result in protective adaptations
in distal femoral articular cartilage.36 Taken together,
these findings suggest that a loading program may
increase the tissue quality of the articular cartilage
of the PFJ. Emerging evidence also suggests that
progressive loading of the PFJ may reduce local
hyperalgesia37 and may alter central pain processing
in individuals with PFP.38,39 Therefore, progressive
quadriceps strengthening may improve a patient’s
envelope of function by enhancing load tolerance of
the PFJ. Clearly, further study is necessary to bet-
ter understand the mechanisms of pain reduction
that are observed in individuals with PFP that result
from a quadriceps strengthening program.
THE BIOMECHANICS OF QUADRICEPS
STRENGTHENING
Prescription of quadriceps strengthening for the
treatment of PFP requires a working knowledge of
the biomechanics of various progressive resistive
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 881
of the quadriceps45 necessitates peak quadriceps
forces estimated at 5 times body weight during the
stance phase of endurance-paced running.46 Muscle
forces of this magnitude are attainable with select
rehabilitation exercises. Single leg squats performed
to at least 65 degrees of knee flexion without added
weight yields peak quadriceps forces of approxi-
mately 4-5 times body weight.47 However, squats to
this depth of knee flexion may result in pain in indi-
viduals with PFP41 and peak knee flexion during run-
ning rarely exceeds 40-45 degrees,47 Thus, clinicians
should opt for added weight to a single leg squat to
attain peak quadriceps that are relevant to running.
Adding resistance to body weight exercises is abso-
lutely required if a clinician wishes to attain peak
quadriceps forces that are of same magnitude as
those seen during jumping. For instance, a bilateral
drop vertical jump results in peak quadriceps forces
of 7 times body weight.48
Provided the added resistance is sufficient, open
kinetic chain knee extension exercises can also
generate peak quadriceps forces that are similar to
forces noted during running and other activities. For
instance, therapists may find it difficult to provide
sport-relevant resistance between 45-90 degrees of
knee flexion41 with the EXT-VR load configuration.
Once past the early stages of rehabilitation, the
constant resistance supplied by a knee extension
machine using the EXT-CR configuration may thus
provide the best means to strengthen the quadri-
ceps between 45-90 degrees of knee flexion in the
athlete recovering from PFP (Figure 3C). For closed
kinetic chain, exercises that involve squatting or leg
presses between 0 and 45 degrees of knee flexion
may be the best means to strengthen the quadri-
ceps with moderate levels of PFJ stress. With either
squatting or open chain knee extension exercises,
clinicians should aim to incrementally increase the
range of motion and level of resistance in response
to improvements in pain in the patient to restore the
envelope of function of the PFJ.
TREATMENTS FOR PROXIMAL
CONTRIBUTIONS TO PATELLOFEMORAL
PAIN
Female athletes with PFP often demonstrate greater
hip adduction, hip internal rotation, and contralat-
eral pelvic drop during sporting tasks.6,49-51 These
sion machines with constant resistance exhibits
PFJ stress values in terminal knee extension that
are proportional to those observed during the same
range of motion with a knee extension with variable
resistance.41 Interestingly, a performing knee exten-
sions between 90-50 degrees of knee flexion with
a constant resistance configuration results in PFJ
stress levels that are intermediate to PFJ stress esti-
mated during closed chain squatting or open chain
knee extension through the same range of motion.41
When selecting appropriate resistance levels, clini-
cians should keep in mind that large internal muscle
forces often result from counteracting much lower
external loads. Regardless of the sport, clinicians
should seek to achieve activity-relevant quadriceps
loads with therapeutic exercise in athletes with PFP
prior to return to sport initiation. During running,
for instance, peak vertical ground reaction forces are
typically around 2.5 times body weight, yet the exter-
nal moment arm acting on the knee is rather large.
In contrast, the much smaller internal moment arm
Figure 2. Patellofemoral joint stress during three different
types of quadriceps strengthening exercises: EXT-VR represents
a free weight attached to the distal lower leg. EXT-CR represents
a knee extension machine that applies constant resistance.
Squat relates to a squatting maneuver. Patellofemoral joint
strees is dependent on the external moment arm, amount of
resistance and the direction of force application. Figure reprinted
with permission from Powers CM, Ho KY, Chen YJ Souza RB,
Farrokhi S. Patellofemoral joint stress during weight-bearing
and non-weight-bearing quadriceps exercises. J Orthop Sports
Phys Ther. May 2014; 44(5): 320-327.
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 882
drop and reposition the femur, via reduced hip adduc-
tion and medial rotation. Smartphone applications
and open source movement analysis software provide
the means to readily analyze an athlete’s mechanics
in the clinic. During running, close proximity of the
medial femoral condyles during midstance (Figure
4), known as a “reduced knee window,”58 is suggestive
of excessive hip adduction and hip internal rotation
of the stance limb. Results of movement analyses can
assist with clinical decision making in developing tar-
geted rehabilitation programs.
Reduced posterolateral hip strength is often observed
in individuals with PFP.1,59 As the posterolateral hip
musculature controls contralateral pelvic drop, hip
mechanics are thought to reduce PFJ contact area,
ultimately resulting in an increase in PFJ stress.50
Real-time magnetic resonance imaging studies sug-
gest relative lateral tracking of the patella as the
femur adducts and internally rotates during a squat-
ting or step down maneuver in females with PFP.52-55
Contralateral pelvic drop is thought to increase ten-
sion in the lateral patellar retinaculum56 via the
iliotibial band,57 potentially contributing to lateral
patellar tracking.
Recent literature has evaluated interventions designed
to address the proximal mechanisms of PFP. Proposed
interventions to address the proximal mechanism
contribution to PFP aim to reduce contralateral pelvic
Figure 3. The interaction between external loads and the external moment arm during common quadriceps strengthening exercises.
Figure 3A: During the single leg squat, the external moment arm (MA) increases as the depth of the squat also increases resulting in
increasing quadriceps forces and patellofemoral joint stress through 90 degrees of knee fl exion. Corresponds with “Squat” in Fig. 2.
Figure 3B: Patient performing open chain knee extension with a weight mounted at the levle of the lower leg (non tap fi gure). The
external moment arm (MA) increases as the knee extends, resulting in increasing quadriceps forces and patellofemoral joint stress as
the knee nears full extension. Corresponds with “EXT-VR” in Fig. 2. Figure 3C: During open chain knee extension on knee extension
machine with a cable and weight stack system, the external moment arm (MA) remains constant throughout the range, resulting in
relatively stable quadriceps forces and patellofemoral joint stress. Corresponds with “EXT-CR” in Fig. 2.
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 883
There is a growing body of evidence of moderate to
high quality that supports the prescription of pos-
terolateral hip strengthening for the treatment of
PFP.6,74 Hip strengthening programs result in moder-
ate to large reductions in PFP with moderate to large
improvements in function in the short- to medium-
term.74 To date, only one study has evaluated long-
term outcomes after a hip strengthening program
for PFP.69 At one-year post-intervention, Fukuda and
colleageus reported that individuals who completed
a hip and quadriceps strengthening program dem-
onstrated greater improvements in PFP and lower
limb function compared with quadriceps strength-
ening alone.69 Evaluating interventions for PFP that
employ hip strengthening can also be challenging
as the quadriceps are also loaded during most hip
strengthening exercises, such as step ups or single leg
squats.68 Future study that delineates hip strength-
ening and quadriceps strengthening exercises is
needed to better understand the mechanism(s) of
pain reduction noted after these rehabilitation pro-
grams. As proximal strengthening does not appear
to alter proximal mechanics, non-biomechanical
mechanisms may explain the reduction in PFP that
is widely reported with rehabilitation programs that
employ hip strengthening.
When approached from a tissue homeostasis perspec-
tive, long-term correction of proximal mechanics
may not be required. As higher levels of hip adduc-
tion75 and internal rotation76 increase PFJ stress,
these mechanics may hinder recovery from PFP.
However, precipitating factor in the development
of PFP in many athletes may be the application of
load beyond the amount that the PFJ has been con-
ditioned to tolerate. For example, a runner may have
always had elevated hip adduction and internal rota-
tion, yet the actual culprit for the development of
PFP may be increasing running mileage faster than
the PFJ and associated structures can adequately
adapt. Along these lines, an athlete who runs with
greater levels of hip adduction and hip internal rota-
tion may be more susceptible to rapid changes in
training loads than a runner who does not exhibit
similar mechanics. Thus, the promising clinical out-
comes of proximal exercise interventions for PFP
may be better explained as simply the systematic
conditioning of the PFJ and supportive musculature
adduction, and hip internal rotation, it is not surpris-
ing that hip strengthening is often prescribed for the
treatment of PFP.6,60,61 Interestingly, posterolateral
hip strengthening does not appear to reduce exces-
sive proximal mechanics in either asymptomatic62,63
or symptomatic individuals.64,65 While these findings
might be surprising, prospective data fail to sup-
port deficits in posterolateral hip strength as a risk
factor for the future development of PFP.59 In fact,
data from two large prospective studies suggest that
individuals who go on to develop PFP actually had
greater posterolateral hip strength.21,66 As reduced
hip strength is observed in individuals with active
PFP, but not before pain develops, hip strength defi-
cits may actually be the result of PFP, rather than
the cause of PFP.59 Also noteworthy, posterolateral
hip strength is not a strong predictor of frontal and
transverse plane hip mechanics during running or
stepdown maneuvers.67
Figure 4. Runner with patellofemoral pain demonstrating
reduced space between the medial femoral condyles i.e., reduced
knee window, suggestive of high levels of hip adduction and hip
internal rotation of the right lower extremity.
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 884
a proximal mechanism during running. This crite-
rion for enrollment in the respective studies under-
scores the importance of a targeted intervention in
response to a thorough clinical gait analysis.58
Cueing a modest increase in step rate (cadence) dur-
ing running has been shown to reduce PFJ contact
forces and stress in individuals with and without
PFP.16,81-83 Clinically, most runners find that employ-
ing modest increases in running cadence is a rela-
tively easy skill to learn. An increase in step rate
by 5-10% over preferred levels reduces PFJ loads in
part by decreasing peak knee flexion and quadriceps
forces during the stance phase of gait.16,81 Again, a
clinical gait analysis is highly recommended in
determining runners who would benefit the most
from an increase in step rate. Specifically, runners
who exhibit high amounts of vertical oscillation of
the estimated center of mass between flight phase
and mid-stance, have footfalls that are far in front of
the estimated center of mass, and reach high levels
of knee flexion during stance phase may benefit the
most from an increase in step rate.81,84 An increase
in step rate also results in a reduction in peak hip
adduction, albeit smaller in magnitude than the
aforementioned kinematic and mirror feedback
to tolerate more load rather than actually changing
hip frontal and transverse plane mechanics.62
MOVEMENT RE-EDUCATION FOR THE
TREATMENT OF PFP
When attempting to restore tissue homeostasis,
reducing PFJ loads through movement re-education
may be particularly helpful in the early to intermedi-
ate stages of rehabilitation. Recent work suggests that
various mechanics associated with PFP are modifi-
able with the use of motor learning techniques. As
a premise for movement re-education for the proxi-
mal mechanism of PFP, individuals with PFP demon-
strated delayed onset and reduced duration of gluteus
medius activation.77,78 Thus, currently described
movement re-education interventions for the proxi-
mal mechanism aim to alter the neuromuscular con-
trol of the gluteal musculature in an effort to control
proximal mechanics, if implicated. In contrast to hip
strengthening, movement re-education has been
shown to reduce proximal mechanics during running
and other functional tasks, such as step descent or a
single leg squat.49 Providing mirror and verbal feed-
back, for instance, has been shown to be effective
at reducing contralateral pelvic drop, hip adduction
and hip internal rotation during a single leg squat.62
Interestingly, changes in proximal mechanics during
a single leg squat did not transfer to running.62 Thus,
patients are able to achieve improved control of proxi-
mal mechanics during common therapeutic exercises
may not necessarily transfer these movement skills
to an unrelated task, such as running. These findings
suggest that changes in lower extremity mechanics
require a motor learning component and that move-
ment retraining likely needs to be task-specific.
The movement re-education literature for the
treatment of PFP has largely focused on retraining
running gait. Proximal mechanics79,80 have been
targeted in published gait retraining studies with
runners with PFP. Realtime kinematic80 or mirror
feedback,79 coupled with verbal cueing, result in
reductions in hip adduction and contralateral pelvic
drop in female runners with PFP (Figure 5). These
reductions in proximal mechanics were accompa-
nied by improvements in reported pain and lower
limb function that were associated with large effect
sizes.49 Importantly, these previous investigations
targeted females with PFP who also demonstrated
Figure 5. Open source software and a webcam can be used to
provide real-time feedback on frontal plane running mechanics.
This video technique is useful if the treadmill has a large con-
troller console that prevents the runner from seeing their refl ec-
tion in a full-length mirror.
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 885
studies.85,86 Thus, running with increased step rate
primarily reduces PFJ forces through a reduction in
quadriceps forces rather than a large effect on lat-
eral tracking of the PFJ.
Adopting a forefoot strike pattern during running
has also been suggested as a means to reduce PFJ
loads.82,87 However, clinicians should be aware, that
conversion to a forefoot strike increases the demand
of the ankle plantarflexors while reducing demand of
theknee extensors. Adopting a forefoot strike pattern
has been shown to result in 11% greater Achilles ten-
don forces per step, which equates to an additional
47.7 times body weight impulse loading of the Achil-
les tendon per mile of running.88 Because adopting a
5-10% increase in running cadence reduces PFJ loads
by 10-20%16,82 while also reducing Achilles tendon
loads,89 cueing an increase in running cadence may be
preferred over adoption of a forefoot running pattern.
Clinical reasoning should guide movement re-educa-
tion prescription. If frontal and transverse plane hip
mechanics are thought to be the main biomechani-
cal factor contributing to a runner’s current PFP, then
visual feedback to cue reductions in these mechanics
are warranted. If sagittal plane running mechanics are
primarily implicated in a runner’s PFP, then cueing an
increase in step rate during running may be the most
effective gait modication. Clinically, cueing a reduc-
tion in proximal mechanics can easily be done with
a full-length mirror or with a live video stream. Sim-
ilarly, cueing an increase in steprate can be accom-
plished via matching the rhythm of a metronome82,86
or in response to real time feedback from commer-
cially available wrist mounted running computers85
that calculate step rate via an accelerometer mounted
in a footpod or within the device itself (Figure 6).
THE ROLE OF FOOT ORTHOSES IN THE
TREATMENT OF PATELLOFEMORAL PAIN
While there appears to be some support for the use
of foot orthoses for the treatment of PFP,90 the bio-
mechanical rationale supporting their use is less
clear. For instance, a 6° medially wedged orthosis
did not reduce peak frontal plane kinematics or
joint moments of the knee or hip in runners with
and without PFP.91 Interestingly, greater standing
calcaneal eversion posture was not predictive of any
changes in frontal plane hip or knee mechanics in
response to orthotics.91 Despite these findings, foot
orthoses, combined with exercise therapy, resulted
in improved outcomes over six weeks in individuals
with PFP compared with exercise therapy alone.90
In an interesting clinical trial, Lewinson and col-
leagues randomized runners with PFP to either
medially or laterally wedged foot orthoses. Regard-
less of foot orthoses assignment, both groups of run-
ners reported 33% reductions in PFP after six weeks
of using the foot orthoses during routine training
runs.92 Non-uniform reductions in frontal plane knee
moments during running with the foot orthoses
were observed across the cohorts.92 These data, con-
sidered along with aforementioned studies, suggest
that foot orthoses may enhance short term outcomes
in PFP rehabilitation programs, but clinical results
may be due to either individualized responses or
non-biomechanical mechanisms. Patients with PFP
who experience a reduction in pain with the use of
foot orthoses may be able to tolerate greater levels
of resistance during therapeutic exercies, potentially
improving their envelope of function.
BIOMECHANICAL CONSIDERATIONS FOR
RETURN TO SPORT
As described previously, peak quadriceps loads asso-
ciated with an athlete’s sport of choice are readily
achieved with targeted resistance exercises. How-
Figure 6. Commercially available running computer enables
the real-time calculation of running cadence (step rate).
The International Journal of Sports Physical Therapy | Volume 11, Number 6 | December 2016 | Page 886
To guide clinical decision making, a criterion-based
progression should be implemented that evaluates
pain during activity and in the 24 hours after the
return to sport session. There are no formal guide-
lines available for acceptable pain in athletes with
PFP completing a return to sport program. Care
should be taken during return to sport tasks to avoid
acute aggravation of knee pain, which can increase
hyperalgesia in individuals with PFP.37 Thus, it is the
authors’ recommendation that pain should remain
at or below 2/10 on the visual analog scale during
return to sport activity, with trace to absent pain
after the activity session.
CONCLUSION
The mechanisms of PFP are complex and enigmatic.
The presentation may be best described by consid-
ering a tissue homeostasis model. Biomechanical
interventions that reduce PFJ loading may be most
helpful during early rehabilitation to allow progres-
sive quadriceps strengthening as tissue homeostasis
is re-established.
Biomechanical considerations should include the
entire kinetic chain including the hip and the ankle,
however the beneficial effects of these interven-
tions may not be the result of long-term biome-
chanical changes. True biomechanical alterations
may be achieved through movement retraining, but
the interventions must be extremely specific to the
desired task.
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... We chose these weights based on our own clinical intuition of current research concepts. 29,41 Specifically, we assigned equal weights to loading peak and impulse considering the need for emphasis on both cumulative and peak loading, 41 whereas no weight was placed on loading rate because there is no current research consensus on its influence on patellofemoral pathomechanics. 29 Each loading index theoretically ranges from 0 to 1, with 0 representing no load and 1 representing an exercise that would have loading peak and impulse both reaching maximum. ...
... We chose these weights based on our own clinical intuition of current research concepts. 29,41 Specifically, we assigned equal weights to loading peak and impulse considering the need for emphasis on both cumulative and peak loading, 41 whereas no weight was placed on loading rate because there is no current research consensus on its influence on patellofemoral pathomechanics. 29 Each loading index theoretically ranges from 0 to 1, with 0 representing no load and 1 representing an exercise that would have loading peak and impulse both reaching maximum. ...
... Sixth, we emphasize again that our choice of loading metric weights was based on our own interpretation of current research concepts. 29,41 These relative weights can be easily modified in the provided worksheet (Appendix, available online), which will automatically update the loading progression order of the 35 exercises according to the user's interpretation of overall patellofemoral joint loading. Our loading metric data and mathematical scheme also serve as a benchmark for future research to identify the mechanistic relationships between patellofemoral pain and other pathologies in the anterior knee structures. ...
Article
Background: Exercises that provide progressive therapeutic loading are a central component of patellofemoral pain rehabilitation, but quantitative evidence on patellofemoral joint loading is scarce for a majority of common weightbearing rehabilitation exercises. Purpose: To define a loading index to quantify, compare, rank, and categorize overall loading levels in the patellofemoral joint across 35 types of weightbearing rehabilitation exercises and activities of daily living. Study design: Descriptive laboratory study. Methods: Model-estimated knee flexion angles and extension moments based on motion capture and ground-reaction force data were used to quantify patellofemoral joint loading in 20 healthy participants who performed each exercise. A loading index was computed via a weighted sum of loading peak and cumulative loading impulse for each exercise. The 35 rehabilitation exercises and daily living activities were then ranked and categorized into low, moderate, and high "loading tiers" according to the loading index. Results: Overall patellofemoral loading levels varied substantially across the exercises and activities, with loading peak ranging from 0.6 times body weight during walking to 8.2 times body weight during single-leg decline squat. Most rehabilitation exercises generated a moderate level of patellofemoral joint loading. Few weightbearing exercises provided low-level loading that resembled walking or high-level loading with both high magnitude and duration. Exercises with high knee flexion tended to generate higher patellofemoral joint loading compared with high-intensity exercises. Conclusion: This study quantified patellofemoral joint loading across a large collection of weightbearing exercises in the same cohort. Clinical relevance: The visualized loading index ranks and modifiable worksheet may assist clinicians in planning patient-specific exercise programs for patellofemoral pain rehabilitation.
... Further, a recent study identified cumulative loading of the patellofemoral joint as a significant contributing factor to PFP (Petersen et al., 2015). Although daily physical activities, such as walking, do not typically result in acute PFP, due to the high frequency of walking in daily life, incorrect movement patterns can lead to an increased cumulative load on the patellofemoral joint, which can disrupt the constant physiological environment within the patellofemoral joint (Willy and Meira, 2016), thereby increasing the risk of PFP (Song et al., 2023). Consequently, a number of studies have investigated the diagnosis and monitoring of gait patterns in patients with PFP with the objective of identifying gait patterns that could be modified with intervention, with the ultimate goal of reducing the symptoms or risk of developing PFP. ...
... This may be attributed to the fact that landing with the knee in an upright position does not effectively cushion the ground reaction forces. The application of higher ground reaction forces to the entire lower limb results in an increased internal load on the knee joint, which in turn induces stress on the patellofemoral joint, leading to the development of PFP (Hughes and Dai, 2023;Willy and Meira, 2016). The other rationale can be attributed to the PFJS calculation model employed in this study. ...
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Purpose This study aimed to analyze the biomechanical characteristics of the lower limb in patients with patellofemoral pain (PFP) while walking under different sensory integration tasks and elucidate the relationship between these biomechanical characteristics and patellofemoral joint stress (PFJS). Our study’s findings may provide insights which could help to establish new approaches to treat and prevent PFP. Method Overall, 28 male university students presenting with PFP were enrolled in this study. The kinematic and kinetic data of the participants during walking were collected. The effects of different sensory integration tasks including baseline (BL), Tactile integration task (TIT), listening integration task (LIT), visual integration task (VIT) on the biomechanical characteristics of the lower limb were examined using a One-way repeated measures ANOVA. The relationship between the aforementioned biomechanical characteristics and PFJS was investigated using Pearson correlation analysis. Results The increased hip flexion angle (P = 0.016), increased knee extension moment (P = 0.047), decreased step length (P < 0.001), decreased knee flexion angle (P = 0.010), and decreased cadence (P < 0.001) exhibited by patients with PFP while performing a VIT were associated with increased patellofemoral joint stress. The reduced cadence (P < 0.050) achieved by patients with PFP when performing LIT were associated with increased patellofemoral joint stress. Conclusion VIT significantly influenced lower limb movement patterns during walking in patients with PFP. Specifically, the increased hip flexion angle, increased knee extension moment, decreased knee flexion angle, and decreased cadence resulting from this task may have increased PFJS and may have contributed to the recurrence of PFP. Similarly, patients with PFP often demonstrate a reduction in cadence when exposed to TIT and LIT. This may be the main trigger for increased PFJS under TIT and LIT.
... Modifications in activities can help lessen the intensity of excessive stresses on the knee joints. Deviations from normal joint mechanics in the lower leg can precipitate patellofemoral pain syndrome, highlighting the importance of prompt attention to these issues (11). Proper positioning of the patella is vital for maintaining stability in the knee joint, emphasizing the need for perfect alignment of the patella within its groove. ...
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Background: Knee pain and patellofemoral syndrome (PFS) are common among athletes, particularly in sports requiring extensive lower limb use such as football. These conditions can significantly impair performance and quality of life. Objective: This study aimed to investigate the prevalence and severity of knee pain and patellofemoral syndrome among football players, and to explore the association between these conditions. Methods: The study was conducted with 145 football players who provided informed consent, in alignment with the Declaration of Helsinki. Data were collected using structured surveys that included the Numeric Pain Rating Scale and the Kujala Scoring questionnaire. The analysis utilized SPSS software (version 25) to conduct descriptive and inferential statistics. Qualitative data were assessed by frequencies and percentages, while quantitative data analysis involved computing means and standard deviations. The association between knee pain and PFS was examined using a Pearson Chi-Square test. Results: The average age of participants was 22.95 years (SD = 2.83), ranging from 19 to 28 years. Regarding knee pain, 8.3% reported no pain, 26.2% mild pain, 32.4% moderate pain, and 33.1% severe pain. For PFS symptoms, 10.3% of players had no symptoms, 27.6% mild, 31.7% moderate, and 30.3% severe symptoms. The Pearson Chi-Square test yielded a p-value of less than 0.05, indicating a significant association between knee pain and the presence of PFS. Conclusion: The study confirmed a significant correlation between knee pain and PFS among football players, highlighting the need for targeted preventive and therapeutic strategies in sports settings to enhance player health and performance.
... Weakness of the hip abductors, lateral rotators, and quadriceps muscles are also common in women with PFP (Glaviano et al., 2019;Neal et al., 2019;Rathleff et al., 2014). Such changes contribute to the increase in load and pressure on the patellofemoral joint, which can contribute to pain (Powers et al., 2017;Willy & Meira, 2016). ...
Article
Objective To verify the effects of replacing exercises targeted on core/hip muscles by exercises targeted on leg/foot muscles in a rehabilitation program for patellofemoral pain (PFP). Design Randomized Controlled Trial. Participants Fifty women with PFP. Methods PFP participants were randomized into the standard rehabilitation group (SRG, n = 25) or distal exercise group (DEG, n = 25). Knee pain, patient-reported function, dynamic knee valgus and muscle strength were measured at baseline and after six and twelve weeks of the program start. Results SRG and DEG presented similar responses to rehabilitation (except for muscle strengthening). Knee pain reduced after 6 weeks (SRG: −37.7%, ES = 1.23; DEG: −30%, ES = 0.93) and 12 weeks (SRG: −47.4%, ES = 1.53; DEG: −43.3%, ES = 1.46). Patient-reported function improved after 6 weeks (SRG: +7.3%, ES = 0.45; DEG: +3.8%, ES = 0.22) and 12 weeks (SRG: +14.1%, ES = 0.80; DEG: +8.8%, ES = 0.50). Dynamic knee valgus reduced after 12 weeks (SRG: −29.7%, ES = 0.38; DEG: −34.5%, ES = 0.32). Both groups experienced increases in knee extension strength (SRG: +9%, ES = 0.28; DEG: +6%, ES = −0.29), but only SRG had strength gains for hip abduction (+10%, ES = 0.36) and extension (+11%, ES = 0.44). Conclusion Exercises targeted on core/hip muscles can be replaced by exercises targeted on leg/foot muscles in a lower limb exercise-based rehabilitation program for women with PFP. Clinical trial registration NCT03663595.
... Weakness of the hip abductors, lateral rotators, and quadriceps muscles are also common in women with PFP (Glaviano et al., 2019;Neal et al., 2019;Rathleff et al., 2014). Such changes contribute to the increase in load and pressure on the patellofemoral joint, which can contribute to pain (Powers et al., 2017;Willy & Meira, 2016). ...
Article
Objectives To evaluate the correlation between isometric muscle strength of the hip abductors (HABD) and lateral rotators (HLR) with the range of motion (ROM) of the pelvis/hip in the frontal/transverse planes, respectively, and between the strength of the knee extensors (KExt) with the ROM of the knee in the sagittal plane during seven tasks. Design Cross-sectional study. Setting Laboratory. Participants Thirty-five women with patellofemoral pain. Main outcome measures Maximum isometric muscle strength of the HABD, HLR, and KExt was measured using a manual dynamometer, and pelvis and lower limbs kinematics were evaluated using 3D optical system during the gait, ascending and descending stairs, the forward and lateral step down tests, and the propulsion and landing phases of the single leg hop test (SLHT). Results A weak correlation was found between KExt strength and knee ROM in the sagittal plane (p = 0.05; r = −0.33) during SLHT landing, and a moderate correlation between HABD strength and ROM of pelvic obliquity (p < 0.01; r = 0.50) during ascending stairs. Conclusions The lower strength of KExt has a weak correlation with higher knee flexion during the landing phase of the SLHT, and the lower strength of HABD has a moderate correlation with lower pelvis ROM in the frontal plane when ascending stairs.
... However, taking into account the improvements in self-reported symptoms observed in the placebo group, it could be speculated that there would also be corresponding alterations in knee biomechanics mediated by this attenuation in pain [61]. Much like alterations in psychological wellbeing, however, improvements in knee mechanics are likely to take longer to manifest than changes in self-reported pain [62]. Regardless, in relation to the effects of the experimental group, this investigation confirms that U.S. grown Montmorency tart cherry supplementation has no effect on proprioception or biomechanical function at the knee joint. ...
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PURPOSE: This study aimed to explore the efficacy of U.S. Montmorency tart cherry in treating recreationally active individuals with patellofemoral pain. METHODS: Twenty-four recreationally active participants with patellofemoral pain were randomly separated into either placebo (males N = 8, females N = 4, age = 43.30 ± 7.86 yrs, mass = 72.10 ± 17.89 kg, stature = 171.16 ± 10.17, BMI = 24.31 ± 3.75 kg/m 2 , symptom duration = 30.18 ± 10.90) or Montmorency tart cherry (males N = 9, females N = 3, age = 41.75 ± 7.52 yrs, mass = 76.96 ± 16.64 kg, stature = 173.05 ± 7.63, BMI = 25.53 ± 4.03 kg/m 2 , symptom duration = 29.73 ± 11.88) groups. Both groups ingested 60 mL of either Montmorency tart cherry concentrate or taste matched placebo daily for 6-weeks. Measures of self-reported pain (KOOS PF), psychological wellbeing (COOP WONCA) and sleep quality (PSQI) alongside blood biomarkers (Creactive protein, uric acid, TNF alpha, creatinine and total antioxidant capacity) and knee biomechanics were quantified at baseline and 6-weeks. Differences between groups were examined using linear mixed effects models. RESULTS: There was 1 withdrawal in the cherry and 0 in the placebo group and no adverse events were noted in either condition. The placebo condition exhibited significant improvements (baseline = 67.90±16.18 & 6-weeks = 78.04±14.83) in KOOS PF scores compared to the tart cherry group (baseline = 67.28±12.55& 6-weeks = 67.55±20.61). No other statistically significant observations were observed. CONCLUSION: Tart cherry supplementation as specifically ingested in the current investigation, does not appear to be effective in mediating improvements in patellofemoral pain symptoms in recreationally active individuals.
Article
Objective To investigate whether meniscal injury leads to the development of patellofemoral (PF) osteoarthritis (PFOA) and to explore how synovitis and gait kinematics mediate this relationship. Methods Fifty-four male Wistar rats (12 weeks old) were randomly assigned to the control, sham, or destabilized medial meniscus (DMM) groups. The rats were subjected to gait analysis to assess the kinematic changes at 2, 4, and 8 weeks postoperatively. Subsequently, the rats were euthanized, and their right knees were harvested for histological analysis. Results The Osteoarthritis Research Society International (OARSI) and modified Mankin (MM) scores in the DMM group were significantly higher than those in the control and sham groups at week 2 and significantly higher than those in the control group at week 4. The OARSI and MM scores in the sham group were significantly higher than those in the control group at weeks 2 and 4. The association between the DMM and OARSI scores was significantly mediated by the synovitis score and knee flexion angle at foot contact (proportion mediated: 58% and 10%, respectively). The association between the sham and OARSI scores was significantly mediated by the synovitis score and knee flexion angle (proportion mediated: 24% and 24%, respectively). Conclusions DMM surgery induced articular cartilage damage in the PF joint. Synovitis and the knee flexion angle significantly mediated the association between DMM or sham surgery and PFOA development.
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The purpose of this study is to give us an insight into the current perceptions held by other professionals who are currently practicing medicine regarding patient referral to physiotherapy. Methods: A self-designed Questionnaire was distributed among the medical practitioners that were currently working various hospitals and clinics which were currently operational and were located in various regions of Lahore, Punjab, Pakistan. The required questionnaires were filled within a period of 3 months. Results: Out of Total 225, 57% were males and 43% were females. Participants on the base of their specialties were 55% from general practice, 45% from medical specialties. The referral rate among the participants showed that 14% participants did not refer any patients at all, 22% Rarely referred patients, 49% referred patients sometimes and 15% participants referred on a regular basis.30% respondents referred patients with a prescription and 70% referred patients with a prescription did not believe that a physiotherapist cannot devise an action plan without proper instruction. While 53% medical doctors included a specified medical diagnosis in their and 47% that include a medical diagnosis said that this was not the cause of including it in referrals.Conclusion: It was concluded that, participants were found to have well response about the patient referral to physiotherapy, the likelihood of referral is good and majority of participants admit physiotherapy as autonomous profession and have opinion that physiotherapist are trained enough to determine the right treatment for their patients. Methods: This is an observational study; cross sectional survey with 306 estimated sample size 288 participants were respondents but remaining 18 were non respondents and data is collected from students of sports sciences department in mentioned universities using Kujala Scoring questionnaire. Data is entered and analyzed using SPSS version 21. Results: The results shows that age of participants were between 19 to 25 years. Number of male (62.15%) participants were more than female (37.85%) participants. prevalence of PFP among sports sciences students is 63.54%( N=183) with mild or no symptoms of anterior knee pain, 26.74%(N=77) with moderate symptoms and 9.72% (N=28) with severe symptoms of Patellofemoral pain syndrome. Conclusion: According to the results we concluded that there is mild or no symptoms of Patellofemoral Pain Syndrome in 63.54 % Sports Sciences Students in Lahore,26.74 % Sport Sciences Students have moderate symptoms of Anterior Knee joint Pain and 9.72% Sports Sciences Students have severe Symptoms of Patellofemoral Pain Syndrome
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Patellofemoral pain syndrome is characterized by severe pain around the knee cap during physical activities. Many researches have been done to describe the causes of PFP and it is found that it is multifactorial in nature. It is suggested that Patellofemoral pain can persist for many years and can cause decline in sports participation. Muscular imbalance and over activity are major causes of knee pain in Sports related PFP .Multiple management strategies are used in the intervention protocol of PFP however, more research is required to find potential causes of knee pain and its management in sport sciences. Objective: The aim of this study is to find out prevalence of Patellofemoral Pain Syndrome among Sports Sciences students in Lahore. Methods: This is an observational study; cross sectional survey with 306 estimated sample size 288 participants were respondents but remaining 18 were non respondents and data is collected from students of sports sciences department in mentioned universities using Kujala Scoring questionnaire. Data is entered and analyzed using SPSS version 21. Results: The results shows that age of participants were between 19 to 25 years. Number of male(62.15%) participants were more than female(37.85%) participants .prevalence of PFP among sports sciences students is 63.54%( N=183) with mild or no symptoms of anterior knee pain, 26.74%(N=77) with moderate symptoms and 9.72% (N=28) with severe symptoms of Patellofemoral pain syndrome. Conclusion: According to the results we concluded that there are mild or no symptoms of Patellofemoral Pain Syndrome in 63.54 % Sports Sciences Students in Lahore,26.74 % Sport Sciences Students have moderate symptoms of Anterior Knee joint Pain and 9.72% Sports Sciences Students have severe Symptoms Of Patellofemoral Pain Syndrome
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A model that takes into account the current workload, and the workload the athlete has been prepared for, as an acute:chronic workload ratio has been previously used as a novel way to monitor training load and injury risk. Fifty-nine elite Australian football players from one club participated in this 2-year study. Global Positioning System technology was used to provide information on running workloads of players. An injury was defined as any non-contact "time-loss" injury. One-week (acute), along with 4-week (chronic) workloads were calculated for a range of variables. The size of the acute workload in relation to the chronic workload was calculated as an acute:chronic workload ratio. An acute:chronic workload ratio of >2.0 for total distance during the in-season was associated with a 5 to 8-fold greater injury risk in the current [relative risk (RR) = 8.65, P = 0.001] and subsequent week (RR = 5.49, P = 0.016). Players with a high-speed distance acute:chronic workload ratio of >2.0 were 5-11 times more likely to sustain an injury in the current (RR = 11.62, P = 0.006) and subsequent week (RR = 5.10, P = 0.014). These findings demonstrate that sharp increases in running workload increase the likelihood of injury in both the week the workload is performed, and the subsequent week.
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OVERUSE INJURY IS A ‘TRAINING LOAD ERROR’ Inappropriately high training loads cause overuse injuries.1 However, it has recently been proposed that overuse injuries should be considered in terms of both ‘overloading’ and ‘underloading’.2 The rationale is that increased injury risk is associated with ‘spikes’ in workload (ie, overloading) and low chronic workloads (ie, underloading), which may leave an athlete predisposed to a ‘spike’ in workload. 3 Given that workload is both modifiable and controllable, it has been suggested that ‘overuse injuries’ be considered as ‘training load errors’.2 4 WHO ‘OWNS’ THE INJURY? Anecdotally, strength and conditioning staff are viewed as the practitioners who ‘break’ the athlete, while medical staff ‘fix’ them. Conversely, conditioning staff may indeed decrease the probability of athletes sustaining an injury by increasing chronic workloads, whereas medical staff may inadvertently increase injury risk by reducing workloads. Given that all coaching staff as well as the performance team (eg, strength and conditioning, sport scientists and physiotherapists) are involved to varying degrees in the training process, an effective solution needs to be multidisciplinary in nature. Periods of underloading and overloading can occur anywhere, from rehabilitation through to game-specific skills and competition, hence communication between athlete, manager and support services is critical to ensure ‘training load errors’ are avoided. In sport, athletes, coaches and performance staff are all responsible for injuries. THE OUT-OF-SEASON ‘BLACK HOLE’ So where does the athlete fit into the process? Some sporting competitions (eg, English Premier League) provide minimal recovery to athletes between seasons, while others (eg, National Rugby League, Australian Football League) can provide athletes with up to an 8-week off-season period. The NFL (American football) provides athletes with a multiweek break at the end of their off-season training, just as they have developed the chronic workloads that may protect against injury. Although athletes are often provided training programmes to perform during these breaks, staff are not permitted to monitor this training, nor are athletes under any obligation to complete it. This period is considered somewhat of a ‘black hole’, as a detailed training history required to provide a systematic return to full training and minimise the risk of injury is unavailable. However, by communicating with athletes, performance staff can identify those who are inadequately prepared for the upcoming planned training loads and appropriate strategies can be put in place to minimise risk. Equally, ensuring athletes have access to suitable training facilities while out-of-season may prevent some of the detraining that occurs during this period. Unfortunately, some athletes return from their off-season ‘holiday’ severely deconditioned, having performed minimal training, thereby increasing their risk of injury.5 The responsibility of the athlete in minimising ‘training load errors’ is rarely acknowledged. Clearly, athletes would benefit from education around the importance of maintaining a minimum chronic workload during their break. NOT ALL TRAINING LOADS CARRY EQUAL RISK The acute:chronic workload ratio is considered a ‘best practice’ approach to monitor athlete workloads.6 An acute: chronic workload ratio of ≥1.5 has been associated with large increases in injury risk.3 7 However, the risk associated with ‘spikes’ in workload are also a function of the chronic workloads performed at that point in time and the acute:chronic workload ratio completed in the previous week. Although high chronic workloads in isolation may protect against injury, the risk of injury is greatest when workload ‘spikes’ occur in combination with either low or high chronic workloads.3 Clearly, not all workloads carry the same risk and a ratio of ≥1.5 should only be viewed as a guide to reduce this risk. Predominantly, analysis of workload ratios covers a period of 4 weeks; however, also worthy of consideration is the sequencing of training sessions within the training week: a high training load could easily be poorly distributed, producing unnecessary ‘spikes’ within a microcycle prior to competition. WHAT ARE WE TRAINING FOR? If everyone involved in the training process has some ‘ownership’ of injuries, how can staff and athletes work together to minimise the risk? The answer most likely lies in understanding the physical demands imposed during all training activities relative to the key demands of competition. In this sense, it is a matter of understanding where the athletes have been, where they are now and where they are going. By quantifying the different training activities, it is possible for athletes, coaches and performance staff to visualise where each of these training activities sit on the workload continuum (figure 1). Importantly, if undertraining increases injury risk,3 6 7 then training that focuses on the average demands of competition results in athletes being underprepared for the most extreme passages of play.8 In this context, if overuse injury is considered a ‘training load error’, then undertraining, and asking athletes to compete in an underprepared state, should be viewed that way as well. AVOIDING GETTING LOST IN THE ‘BERMUDA TRIANGLE’ Often, there is somewhat of a ‘Bermuda Triangle’ among coaches, strength and 1School of Human Movement Studies, University of Queensland, Brisbane, Queensland, Australia; 2School of Exercise Science, Australian Catholic University, Brisbane, Queensland, Australia; 3New York Football Giants, New Jersey, USA; 4Cleveland Browns, Ohio, USA; 5Manchester United Football Club, Manchester, UK; 6Liverpool Football Club, Liverpool, UK; 7Department of Life Sciences, University of Roehampton, London, UK; 8Sports Surgery Clinic, Dublin, Ireland; 9Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar; 10Football Research Group, Linkoping University, Linkoping, Sweden; 11Division of Community Medicine, Department of Medical and Health Sciences, Linkoping University, Linkoping, Sweden; 12UEFA Medical Committee, Nyon, Switzerland Correspondence to Dr Tim J Gabbett, School of Exercise Science, Australian Catholic University, Brisbane, QLD 4014, Australia; tim_gabbett@yahoo. com.au Gabbett TJ, et al. Br J Sports Med Month 2016 Vol 0 No 0 1 Editorial BJSM Online First, published on June 1, 2016 as 10.1136/bjsports-2016-096308 Copyright Article author (or their employer) 2016. Produced by BMJ Publishing Group Ltd under licence. Downloaded from http://bjsm.bmj.com/ on June 1, 2016 - Published by group.bmj.com conditioning and medical staff; they may understand their own roles well, but possibly lack an appreciation of the role that others play within the team. Working in isolation increases the risk of the athlete getting ‘lost’ in the ‘Bermuda Triangle’, ultimately increasing injury risk. Having an appreciation of the interdependency of the role of all ‘players’ in the on-field and off-field ‘team’, as well as efficient communication streams, is critical towards reducing injuries that occur as a result of training load errors. Twitter Follow Tim Gabbett at @timgabbett; Steve Kennelly at @stevekennelly; Jordan Milsom at milsomlfc; Enda King at @enda_king; Rod Whiteley at @rodwhiteley and Jan Ekstrand at @janekstrand Contributors TJG was responsible for the initial concept of the manuscript. All the authors contributed equally to writing the manuscript. Competing interests None declared. Provenance and peer review Not commissioned; externally peer reviewed. To cite Gabbett TJ, Kennelly S, Sheehan J, et al. Br J Sports Med Published Online First: [ please include Day Month Year] doi:10.1136/bjsports-2016-096308 Accepted 12 May 2016 Br J Sports Med 2016;0:1–2. doi:10.1136/bjsports-2016-096308
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Background: It has been previously shown that exercise programs for patellofemoral pain syndrome (PFPS) can be supported by medially directed taping. Evidence supporting the use of patellar braces is limited because previous studies have been low quality. The aim of this study is to compare the outcomes of patients with PFPS after treatment with a medially directed patellar realignment brace and supervised exercise. Methods: In a prospective randomized multicenter trial, 156 patients with PFPS were included and randomly assigned to 6 weeks of supervised physiotherapy in combination with the patellar realignment brace, or supervised physiotherapy alone. Outcome measures were the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales, numeric analog pain scores, and the Kujala score at baseline, 6 weeks, 3 months, and 1 year after the start of therapy. The patient's self-reported perception of recovery was also assessed at these points. Results: Both treatment groups showed a significant improvement in all outcome measures over the study period. After 6 and 12 weeks of therapy, patients in the brace group had significantly higher KOOS sub-scale scores, a higher mean Kujala score, and less pain while climbing stairs or playing sports. After 54 weeks a group difference could be only detected for the KOOS ADL sub-scale. Conclusion: The use of a medially directed realignment brace leads to better outcomes in patients with PFPS than exercise alone after 6 and 12 weeks of treatment. After 1 year of follow-up this positive effect diminished.
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Achilles tendon (AT) injuries are common in runners. The AT withstands high magnitudes of stress during running which may contribute to injury. Our purpose was to examine the effects of foot strike pattern and step frequency on AT stress and strain during running utilizing muscle forces based on a musculoskeletal model and subject specific ultrasound-derived AT cross sectional area. Nineteen female runners performed running trials under six conditions including rearfoot strike and forefoot strike patterns at their preferred cadence, +5%, and -5% preferred cadence. Rearfoot strike patterns had less peak AT stress (P<.001), strain (P<.001), and strain rate (P<.001) compared to the forefoot strike pattern. A reduction in peak AT stress and strain were exhibited with a +5% preferred step frequency relative to the preferred condition using a rearfoot (P<.001) and forefoot (P=.005) strike pattern. Strain rate was not different (P>.05) between step frequencies within each foot strike condition. Our results suggest that a rearfoot pattern may reduce AT stress, strain, and strain rate. Increases in step frequency of 5% above preferred, regardless of foot strike pattern, may also lower peak AT stress and strain.
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Background: There is dogma that higher training load causes higher injury rates. However, there is also evidence that training has a protective effect against injury. For example, team sport athletes who performed more than 18 weeks of training before sustaining their initial injuries were at reduced risk of sustaining a subsequent injury, while high chronic workloads have been shown to decrease the risk of injury. Second, across a wide range of sports, well-developed physical qualities are associated with a reduced risk of injury. Clearly, for athletes to develop the physical capacities required to provide a protective effect against injury, they must be prepared to train hard. Finally, there is also evidence that under-training may increase injury risk. Collectively, these results emphasise that reductions in workloads may not always be the best approach to protect against injury. Main thesis: This paper describes the 'Training-Injury Prevention Paradox' model; a phenomenon whereby athletes accustomed to high training loads have fewer injuries than athletes training at lower workloads. The Model is based on evidence that non-contact injuries are not caused by training per se, but more likely by an inappropriate training programme. Excessive and rapid increases in training loads are likely responsible for a large proportion of non-contact, soft-tissue injuries. If training load is an important determinant of injury, it must be accurately measured up to twice daily and over periods of weeks and months (a season). This paper outlines ways of monitoring training load ('internal' and 'external' loads) and suggests capturing both recent ('acute') training loads and more medium-term ('chronic') training loads to best capture the player's training burden. I describe the critical variable-acute:chronic workload ratio)-as a best practice predictor of training-related injuries. This provides the foundation for interventions to reduce players risk, and thus, time-loss injuries. Summary: The appropriately graded prescription of high training loads should improve players' fitness, which in turn may protect against injury, ultimately leading to (1) greater physical outputs and resilience in competition, and (2) a greater proportion of the squad available for selection each week.
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Objectives: To explore the role of muscular strength and imbalance as predisposing factors in the development of anterior knee pain syndrome(AKPS). Methods: 96 male military recruits without history of knee pain volunteered for the study. Each volunteer underwent an isokinetic test prior to the start of a strenuous training program (approximately 8 to 12 hours/day for 6 weeks). The isokinetic test consisted of concentric contractions of the knee flexors and extensors at 60°/s and 240°/s. A detailed history and clinical examination of the patellofemoral joint was performed on each recruit. Independent sample t-tests were used to compare the isokinetic muscle parameters in recruits who developed AKPS during the training (pathological group) and in those who did not (control group). Binary logistic regression analysis was used to define the predictive outcome of anthropometrics and the isokinetic parameters for the development of AKPS. Results: 31 recruits developed AKPS. Absolute and bodyweight normalized peak extensor torque at 60°/s was significantly lower in the pathological group in comparison to the control group. Significant lower peak torque/BMI (Body Mass Index) were also indicated at both velocities. Recruits who developed AKPS had a shorter stature. No regression model could be set up to give any predictive value to the analyzed parameters. Conclusions: Recruits with shorter stature and lower quadriceps strength are more prone to develop AKPS during BMT. However, as the etiology of AKPS is multifactorial these parameters alone may not suffice to predict the occurrence of this pathology. On the other hand, the results of this study emphasize the importance of the reinforcement of quadriceps strength in the treatment and prevention of AKPS.
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Abstract Anterior cruciate ligament (ACL) injury can be a painful, debilitating and costly consequence of participating in sporting activities. Prophylactic knee bracing aims to reduce the number and severity of ACL injury, which commonly occurs during landing maneuvers and is more prevalent in female athletes, but a consensus on the effectiveness of prophylactic knee braces has not been established. The lower-limb muscles are believed to play an important role in stabilizing the knee joint. The purpose of this study was to investigate the changes in lower-limb muscle function with prophylactic knee bracing in male and female athletes during landing. Fifteen recreational athletes performed double-leg drop landing tasks from 0.30 m and 0.60 m with and without a prophylactic knee brace. Motion analysis data were used to create subject-specific musculoskeletal models in OpenSim. Static optimization was performed to calculate the lower-limb muscle forces. A linear mixed model determined that the hamstrings and vasti muscles produced significantly greater flexion and extension torques, respectively, and greater peak muscle forces with bracing. No differences in the timings of peak muscle forces were observed. These findings suggest that prophylactic knee bracing may help to provide stability to the knee joint by increasing the active stiffness of the hamstrings and vasti muscles later in the landing phase rather than by altering the timing of muscle forces. Further studies are necessary to quantify whether prophylactic knee bracing can reduce the load placed on the ACL during intense dynamic movements.
Article
Study Design Level 4: Controlled laboratory study. Background Little is known regarding potential differences between treadmill and overground running in regards to patellofemoral joint and Achilles tendon loading characteristics. Objectives We sought to compare measures of loading to the patellofemoral joint and Achilles tendon across treadmill and overground running in healthy, uninjured runners. Methods Eighteen healthy runners ran at their self-selected speed on an instrumented treadmill and overground while three-dimensional running mechanics were sampled. A musculoskeletal model derived peak load, rate of loading and estimated cumulative load per 1 kilometer of continuous running for the patellofemoral joint and Achilles tendon for each condition. Data were analyzed via paired T-tests and Pearson’s correlations to detect differences and assess relationships, respectively, between the two running mediums. Results No differences (p>0.05) were found between treadmill and overground running for the peak, the rate of loading, or estimated cumulative patellofemoral joint stress per 1 kilometer of continuous running. However, treadmill running resulted in 12.5% greater peak Achilles tendon force (p<0.001), 15.6% greater loading rate of Achilles tendon force (p<0.001) and 14.2% greater estimated cumulative Achilles tendon force per 1 kilometer of continuous running (p<0.001) compared with overground running. There were strong (r>0.70) and moderate agreements (r>0.50) for most patellofemoral joint and Achilles measures, respectively, between treadmill and overground running. Conclusions No differences were observed in loading characteristics to the patellofemoral joint between running mediums, yet treadmill running resulted in greater Achilles tendon loading compared with overground running, Future investigations should determine if sudden bouts of treadmill running places the Achilles tendon at risk for mechanical overload in runners who habitually train overground. J Orthop Sports Phys Ther, Epub 12 May 2016. doi:10.2519/jospt.2016.6494
Article
Objective. Compare pressure pain thresholds (PPTs) at the knee and a site remote to the knee in female adults with patellofemoral pain (PFP) to pain-free controls before and after a patellofemoral joint (PFJ) loading protocol designed to aggravate symptoms. Design. Cross-sectional study Setting. Participants were recruited via advertisements in fitness centers, public places for physical activity and universities. Subjects. Thirty-eight females with patellofemoral pain, and 33 female pain-free controls. Methods. All participant performed a novel PFJ loading protocol involving stair negotiation with an extra load equivalent 35% of body mass. PPTs and current knee pain (measured on a visual analogue scale) was assessed before and after the loading protocol. PPTs were measured at four sites around the knee and one remote site on the upper contralateral limb. Results. Females with PFP demonstrated significantly lower PPTs locally and remote to the knee, both before and after the PFJ loading protocol when compared to control group. Following the loading protocol, PPTs at knee were significantly reduced by 0.54 kgf (95%CI = 0.33; 0.74) for quadriceps tendon, 0.38 kgf (95%CI = 0.14; 0.63) for medial patella, and 0.44 kgf (95%CI = 0.18; 0.69) for lateral patella. No significant change in PPT remote to the knee was observed – 0.10 kgf (95%CI = −0.04; 0.24). Conclusions. Female adults with PFP have local and widespread hyperalgesia compared to pain free controls. A novel loading protocol designed to aggravate symptoms, lowers the PPTs locally at the knee but has no effect on PPT on the upper contralateral limb. This suggests widespread hyperalgesia is not affected by acute symptom aggravation.
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Running biomechanics play an important role in the development of injuries. Performing a running biomechanics analysis on injured runners can help to develop treatment strategies. This article provides a framework for a systematic video-based running biomechanics analysis plan based on the current evidence on running injuries, using 2-dimensional (2D) video and readily available tools. Fourteen measurements are proposed in this analysis plan from lateral and posterior video. Identifying simple 2D surrogates for 3D biomechanic variables of interest allows for widespread translation of best practices, and have the best opportunity to impact the highly prevalent problem of the injured runner.