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Masterclass
Task based rehabilitation protocol for elite athletes following Anterior
Cruciate ligament reconstruction: a clinical commentary
Lee Herrington
a
,
*
, Gregory Myer
b
, Ian Horsley
c
a
Directorate of Exercise, Sport and Physiotherapy, Allerton Building, University of Salford, Salford, Greater Manchester M6 6PU, UK
b
Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA
c
English Institute of Sport, Sportcity, Manchester M11 3FF, UK
article info
Article history:
Received 17 April 2013
Received in revised form
30 July 2013
Accepted 2 August 2013
Keywords:
ACLR
Rehabilitation
Criteria
abstract
Anterior Cruciate ligament (ACL) injuries are one of the most common and devastating knee injuries
sustained whilst participating in sport. ACL reconstruction (ACLR) remains the standard approach for
athletes who aim to return to high level sporting activities but the outcome from surgery is not assured.
Secondary morbidities and an inability to return to the same competitive level are common following
ACLR. One factor which might be linked to these sub-optimal outcomes may be a failure to have clearly
defined performance criteria for return to activity and sport. This paper presents a commentary
describing a structured return to sport rehabilitation protocol for athletes following ACLR. The protocol
was developed from synthesis of the available literature and consensus of physiotherapists and strength
and conditioning coaches based in the home country Institute of Sports within the United Kingdom.
!2013 Elsevier Ltd. All rights reserved.
1. Introduction
Anterior Cruciate ligament (ACL) injuries are one of the most
common and devastating knee injuries sustained whilst partici-
pating in sport. ACL reconstruction (ACLR) remains the standard
approach for athletes who aim to return to high level sporting ac-
tivities (Hewett, Di Stasi, & Myer, 2013). Less than half of athletes
who undergo ACLR are able to return to sport within the first year
post surgery (Ardern, Webster, Taylor, & Feller, 2011), on return
around 25% of the athletes returning to sport will have a subse-
quent second ACL injury (Hui et al., 2011; Leys, Salmon, Waller,
Linklater, & Pinczewski, 2012), with the outcomes from second
surgery being considerably worse (Spindler et al., 2011). Not only
do these athletes returning to sport have a 1 in 4 chance of re-
injuring an ACL, but regardless of whether they return to sport or
not have a 1 in 2 chance of developing significantly clinical and
radiological osteoarthritis (OA) of both the tibiofemoral and
patellofemoral joints within 10e15 years (Crossley & Hinman, 2011;
Culvenor, Cook, Collins, & Crossley, 2012; Oiestad, Holm,
Gunderson, Myklebust, & Risberg, 2010). It would appear despite
the advances in surgical technique and rehabilitation that the post-
operative problems of these patients are not being fully addressed
(Hewett et al., 2013).
Current practice around ACLR rehabilitation is quite disparate
and inconsistent due to the lack of clear consistent sequential
functional progressions aimed at achieving task specific goals. The
current criteria for return to sport are both vague and rely on
personal interpretation with the literature lacking empirically
based criteria (Schmitt, Paterno, & Hewett, 2012). There is an
absence of, or clear criteria for progression within the rehabilitation
literature, a typical example would be from Wilk, Macrina, Cain,
Dugas, and Andrews (2012) “once satisfactory strength and
neuromuscular control has been demonstrated..functional ac-
tivities such as running and cutting may begin 12 weeks and 16e18
weeks after surgery respectively”. Rarely if ever are the terms
“satisfactory strength and neuromuscular control”defined. When
objective criteria for return to sports such as hop tests and strength
symmetry ratios of hamstrings and quadriceps compared to
contralateral side, are offered as a minimal standard to achieve,
these are clearly not detailed enough when dealing with athletes
aiming for return to high level competitive sports after ACLR
(Bizzini, Hancock, & Ellizzeri, 2012; Van Grinsven, van Cingel, Holla,
& van Loon, 2010). The present criteria used for return to sport
would appear to need to be revisited, especially as recurrent injury
seems to be an increasing problem (Renstrom, 2013).
*Corresponding author. Tel.: þ44 161 295 2326.
E-mail addresses: l.c.herrington@salford.ac.uk (L. Herrington), greg.myer@
cchmc.org (G. Myer), ian.horsley@eis2win.co.uk (I. Horsley).
Contents lists available at ScienceDirect
Physical Therapy in Sport
journal homepage: www.elsevier.com/ptsp
1466-853X/$ esee front matter !2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.ptsp.2013.08.001
Physical Therapy in Sport 14 (2013) 188e198
In the absence of clear goals any exercise rehabilitation inter-
vention lacks focus and is likely to be less efficient and effective at
returning the athlete both safely and quickly (on time) to sport and
with reduced risk of re-occurrence or secondary morbidity. Estab-
lishing clear goals should aid both the athlete and the coach in
seeing progression during what is a prolonged rehabilitation
period, it allows those delivering the rehabilitation to the athlete to
progress when targets are being met and hold and/or consolidate
when they are not. It also removes the current practice of time
based goals which often do not reflect the athlete’s functional
ability at the time they are reached. An example of this being that
often athletes following UK based ACLR post-operative protocols,
are not allowed to run in any form until 3 months post-operation. In
terms of graft healing and maturation, the often cited reason for
determining this figure, this is an irrelevant date (Claes, Verdonk,
Forsyth, & Bellemans, 2011; Woo, Abramowitch, Kilger, & Liang,
2006), however this becomes a fixed point in the athlete,
coaches, surgeons and rehabilitation specialists minds with the
athlete failing if they cannot run at that point and on track if they
are running at this time. Yet, as all practitioners realize the ability to
return to running successfully is related not to healing time post-
operation but on the attainment of a number of task specific skills
and functional goals, if rehabilitation is geared toward these then
this would allow this the athlete to be “ready when they are ready”
and the multitude of intermediate markers will allow the practi-
tioner to know exactly when they can achieve this safely.
In their reflection current issues relating to ACL injury and
reconstruction Hewett et al. (2013) commented that the majority of
athletes who have ACL reconstruction do not successfully return to
sport and even those that do rarely are able to perform at the same
level in subsequent seasons after they have returned (Ardern et al.
2011). Often the literature reports outcomes from American colle-
giate or varsity athletes, though often training full time and re-
ceiving full medical and rehabilitative support, these athletes
may still not fully represent high performance “professional’
athletes.
The data on elite as opposed to varsity or collegiate sport pre-
sents a more mixed picture with Busfield, Kharrazi, Starkey,
Lombardo, and Seegmiller (2009) reporting only 22% of national
basketball association (NBA) players failed to returned to play, but
of the 78% who returned, 44% were not performing at the same
level, based on match statistics. Similarly, in the national football
league (NFL) Shah, Andrews, Fleisig, McMichael, and Lemak (2010)
found 63% of players returned to play. In a more detailed analysis of
NFL players Carey, Huffman, Parekh, and Sennett (2006) found just
under 80% of players returned to sport but this on average tookover
12 months, and these players had typically performances deficits in
the region of 30% based on match statistical data. In women’s
professional basketball Namdari, Scott, Milby, Baldwin, and Gwo-
Chin (2011) found 78% of players returned to sport, but again
there was a significant reduction in a number of sport specific game
skill statistics. Athletes in high performance professional sport
would appear to return to sport in greater numbers than their
counterparts in varsity or collegiate sport, there is insufficient data
to comment on the comparative longer term outcomes. But, what
appears to be clear is that these athletes even on return to sport do
not have the same impact on the games they play.
One of the main reasons for this could be the failure of the
athletes to regain their pre-injury neuromuscular function (Paterno
et al., 2010; Thomee et al., 2011). In a recent review paper Ardern
et al. (2011) concluded that even though 85e90% of athletes ob-
tained normal (or near normal) strength values the return to sport
rate was still low. The failure to return may be related to fear of re-
injury or lack of confidence with both Lentz et al. (2012) and
McCulloch et al. (2012) in a similar group collegiate and varsity
athletes reporting these factors to be significant in 50% of patients
who failed to return to the same level of sport. Furthermore, with
Lentz et al. (2012) finding the other major factor being continued
knee symptoms, it may be that the patients’rehabilitation is failing
to meet their needs for a complete non-problematic returnto sport.
This could be either in terms of the components of the rehabilita-
tion programmes, the way they are monitored and progressed or
the criteria used to measure aspects such as suitability to return to
sport. There seems to be a disconnect between patients self-
reported outcomes, rating their performance and their muscle
functional capacity (Thomee et al., 2011). This could be because of a
lack of sensitivity of the methods currently used in testing muscle
function or the need for more exacting and challenging perfor-
mance tests (Thomee et al., 2011).
Insufficient neuromuscular control during dynamic movements
has been suggested to be a major factor in both primary (Hewett
et al., 2005; Zazulak, Hewett, Reeves, Goldberg, & Cholewicki,
2007) and secondary (post-surgical) (Paterno et al., 2010) ACL
injury risk. During various landing and cutting tasks excessive knee
abduction moments (Hewett et al., 2005) and frontal plane trunk
displacement (Zazulak et al., 2007) have both been predictive of
ACL injury. Paterno et al. (2010) found these motion asymmetries
and poor movement strategies persisted even following return to
sport and were highly predictive of secondary ACL injury. It would
appear that rehabilitation needs to be geared at least in part to
regaining symmetrical motion and appropriate movement strate-
gies to reduce risk of re-injury and improve function.
The literature around the outcome from ACLR surgery would
appear to indicate that a high proportion of athletes do not return
to the same level of sport, in the medium term, have increased
risk of re-injuring the reconstructed or the contralateral knee and
in the longer term of developing osteoarthritis within both the
tibiofemoral and patellofemoral joints. It may be in part that these
relatively poor outcomes are due to a failure to fully rehabilitate
these athletes and assess them with sufficiently rigorous criteria
before they pass through the stages of rehabilitation on route to
return to sport. Here the failure to rehabilitate could either expose
the athlete to deleterious loads they are not physically able to
control, not prepared for the demands of the sport so they are
physically incapable of returning or alternately the lack of rigor in
the testing has left the athlete lacking confidence in their ability to
return.
This contention is strongly supported by the literature which
indicates that with the rate of return to sport being low, it would
suggest that the tests commonly used as criteria to return athletes
to unrestricted sports activities are not demanding enough or
variables more important for safe return to unrestricted sports
activities are not being evaluated post-surgically (Angelozzi et al.,
2012; Chmielewski, 2011). Currently, based on objective criteria,
there is no consensus as to when athletes should safely return to
their pre-injury sport level after ACLR, especially in sports activities
that require high levels of dynamic neuromuscular control coupled
with power generation and absorption (Angelozzi et al., 2012;
Myer, Brent, Ford, & Hewett, 2011; Myer, Paterno, Ford, Quatman,
& Hewett, 2006). With this in mind a consensus group was set up
representing physiotherapists and strength and conditioning
coaches from the United Kingdom Institutes of Sport chaired by a
recognized international expert in the field of ACL injury and
rehabilitation research. The aim of this consensus group was to
develop a robust set of progression criteria and concurrently
running rehabilitation guidelines for the management of ACLR
patients within the UK Institute of Sport Environment. The specific
goal being to agree on a series of generic markers for progression
for each of rehabilitation stages along with monitoring tools to
assess loading stress on the athlete’s knee.
L. Herrington et al. / Physical Therapy in Sport 14 (2013) 188e198 189
2. Rehabilitation stages
The consensus group identified the following stages for the
ACLR patient to progress through in their journey to return to their
sport.
"Pre-operative
"Post-operative recovery
"Progressive limb loading
"Unilateral load acceptance
"Sport specific task training
"Unrestricted sport specific training
For each of these phases the group identified key criteria (and
specific tests) which were to be achieved prior to the athlete being
released to move on to the next rehabilitative phase. Within each of
these phases the group also identified typical rehabilitation activ-
ities required to achieve these goals.
2.1. Monitoring
Alongside the end of rehabilitation stage criteria, the athlete
whilst undertaking the rehabilitation programme needs to be
monitored within each session, daily and weekly for certain key
performance indicators. These measurements relate to the impact
of the rehabilitation exercises on the patients knee, assessing if the
knee is becoming stressed by the level of loading. The athlete is
monitored continuously both for the effect of the quantity of
rehabilitation activity and the quality of performance of the reha-
bilitation activities.
2.2. Monitoring the effect of rehabilitation exercise load
Pain and swelling can be used to determine exercise progression
as these factors will relate to the loading stresses which have been
placed on the knee (Myer, Brent, Ford, & Hewett, 2008). Measure-
ment of knee circumference at the patella has been shown to have
strong intra-tester reliability and good sensitivity to change
(Jakobsen, Christensen, Christensen, Olsen, & Bandholm, 2010);
therefore the impact of rehabilitation and activities of daily living
are monitored by changes in knee circumference. Jakobsen et al.
(2010) showed changes of greater than 1 cm to be clinically sig-
nificant. In practice the patient measures knee circumference on
first rising and at the end of the day, the change in this score
(greater than 1 cm) being an indicator of a significant increase in
effusion within the knee (Jakobsen et al., 2010). Similarly, pain can
be monitored using a 10 point numeric rating scale (0 ¼no pain,
10 ¼worst imaginable pain), this has been shown to be sensitive to
changes in pain which effect function (Krebs, Carey, & Weinberger,
2007) with a reduction or increase by 1 point being regarded as the
minimal clinically important change (Salaffi, Stancati, Silvestri,
Ciapetti, & Grassi, 2004). In practice the patient reports pain on
first rising and weight bearing, following any and all rehabilitation
sessions and prior to going to bed. Any change in score from the
previous day is noted and significant increases in post rehabilita-
tion scores (>1) which do not resolve by the evening.
2.3. Monitoring of performance quality; single-leg loading
qualitative assessment tool (QASLS)
Insufficient neuromuscular control during dynamic movements
has been suggested to be a major factor in both primary (Hewett
et al., 2005; Zazulak et al., 2007) and secondary (post-surgical)
(Paterno et al., 2010) ACL injury risk. During various landing and
cutting tasks excessive knee abduction moments (Hewett et al.,
2005) and frontal plane trunk displacement (Zazulak et al., 2007)
have both been predictive of ACL injury and so also may relate to
increase stress loading and potential graft failure in the ACLR pa-
tients. Paterno et al. (2010) found these motion asymmetries and
poor movement strategies persisted even following return to sport
and were highly predictive of secondary ACL injury.
It would appear that rehabilitation needs to be geared at least in
part to regaining symmetrical motion and appropriate movement
strategies to reduce risk of re-injury and improve function. In order
to carry this out a means of monitoring limb alignment during
functional tasks is required. Within the literature limb alignment
control has been assessed using what has been regarded as the
“gold standard”3D motion capture (Hewett et al., 2005). These
systems although accurate are expensive and the assessments time
consuming (Onate, Cortes, Welch, & Van Lunen, 2010), and not
practical to use in the clinical environment for monitoring within
session performance. This has led a number of authors to develop
qualitative means of assessing lower limb alignment (Chmielewski
et al., 2007; Crossley, Zhang, Schache, Bryant, & Cowan, 2011;
Ekegren, Miller, Celebrini, Eng, & Macintyre, 2009; Onate et al.,
2010; Whatman, Hing, & Hulme, 2012).
The findings of these studies have shown their scoring systems
to be both reliable (Chmielewski et al., 2007; Crossley et al., 2011;
Ekegren et al., 2009; Onate et al., 2010; Whatman et al., 2012)
and valid (Ekegren et al., 2009;Onate et al. 2010;Whatman, Hulme,
& Hing, 2013) and thus show considerable promise when assessing
patients. To date these qualitative scoring systems have either
assessed bilateral drop jumps (Ekegren et al., 2009; Onate et al.,
2010; Padua et al., 2009) or single-leg squatting (Chmielewski
et al., 2007; Crossley et al., 2011; Whatman et al., 2012), with
Fig. 1. Qualitative scoring sheet for all single-leg loading tasks.
L. Herrington et al. / Physical Therapy in Sport 14 (2013) 188e198190
none assessing single-leg landing tasks or using a single system to
assess diverse tasks. Having a single assessment system across all
single-leg loading tasks is likely to improve usability for the clini-
cian as well as reliability as experience and practice improve reli-
ability (Whatman et al., 2012).
A qualitative scoring system was devised by one of authors (LH)
based on the previously reported scoring systems of Crossley et al.
(2011) and Whatman et al. (2012, 2013). It involved dichotomous
scoring of the movement strategy occurring in individual body
regions (arm, trunk, pelvis, thigh, knee, foot). Scoring was defined
as a zero for appropriate strategy and one for inappropriate
movements, for each region with best overall score being 0 and
worst 10 points. The scoring sheet is shown in Fig. 1 and examples
of appropriate and inappropriate movement strategies in Fig. 2. The
qualitative scoring system used was based on those previously
reported in the literature which had attempted to analyze single-
leg squat and had shown good to excellent intra and intertester
reliability (Crossley et al., 2011; Whatman et al., 2012). The scheme
incorporated region criteria similar to that used by both Crossley
et al., 2011 and Whatman et al. (2012), following the assertion
from both Chmielewski et al. (2007), Onate et al. (2010) and
Whatman et al. (2012) that this increased content validity. The
scheme used was modified from those studies to also take into
account trunk and pelvis motion which Crossley et al. (2011), Myer
et al. (2008) and Whatman et al. (2013) regarded as a significant
factor in the alteration of lower limb alignment and load. Similarly,
a dichotomous scale was used when classifying motion within each
of the regions which was shown to increase reliability (Whatman
et al., 2012).
The qualitative scoring system used (QASLS) has been shown to
have excellent validity when compared to 3D motion capture ki-
nematics during single-leg squatting and landing (Herrington &
Munro, in press), excellent intra and intertester reliability
(Almangoush, Herrington, & Jones, in press; Dawson & Herrington,
in press) and strong reliability when assessing real time versus
video analysis of single-leg squat (Dawson & Herrington, in press).
Fig. 2. Examples of optimal and sub-optimal strategies during single-leg loading tasks.
L. Herrington et al. / Physical Therapy in Sport 14 (2013) 188e198 191
The qualitative assessment of the athlete performing their reha-
bilitation exercises would then be informally assessed during all
rehabilitation sessions using the criteria and formal assessed as a
progression criterion within the stages outlined below.
2.4. Pre-operative phase
2.4.1. Aim
Prepare the athlete for surgery, normalizing knee function
through minimizing knee effusion, gaining full quadriceps activa-
tion and normal gait.Typical rehabilitation activities
"Effusion control
"Muscle activation
"Range of movement
"Gait re-education
"Limb loadingTargets for the patient prior to surgery
"Full quadriceps activation (no lag on straight leg raise (SLR))
"Full range of movement (symmetrical)
"Minimal activity related effusion (<1 cm change supra patella
circumferential measurement)
"Leg press limb symmetry index (LSI) equals less than 5%
BLSI ¼(involved side/uninvolved side) $100
"Normal gait walk and straight line jogging (8e10 min/mile)
"Functional questionnaire score (Knee Outcome Osteoarthritis
Score (KOOS), International Knee Documentation committee
(IKDC) subjective form etc.) equal to or greater than normative
valuesRationale for pre-operative phase targets
"Full quadriceps activation (no lag on straight leg raise (SLR))
Activation failure of the quadriceps has been shown to
contribute to profound strength deficits in patients with knee joint
pathology and may serve as a barrier to rehabilitation of quadriceps
post-operatively (Adams, Logerstedt, Hunter-Giordano, Axe, &
Synder-Mackler, 2012; Lynch, Logerstedt, Axe, & Snyder-Mackler,
2012).
"Full range movement (symmetrical)
Limited pre-operative range of movement has been shown to
significantly limit the progression of post-operative rehabilitation
(Adams et al., 2012; Quelard et al., 2010)
"Minimal increase in activity related effusion (<1 cm change
knee circumference over patella)
Changes in knee joint effusion are frequently associated with
irritation of intra-articular structures, articular disorders and clin-
ically active knees (Hurley, 1997). The level of effusion has been
strongly associated with quadriceps inhibition; increasing effusion
creating greater inhibition (Palmieri-Smith, Thomas, & Woitys,
2008). The level of pre-operative joint effusion has been impli-
cated in development of early post-operative quadriceps activation
failure (Lynch et al., 2012) and increased risk of post-operative
arthrofibrosis (Rubin, Yeh, & Medvecky, 2009). The subjective
grading of effusion (Sturgill, Snyder-Mackler, Manal, & Axe, 2009)
would appear to show no relationship to central activation ratio of
the quadriceps (Lynch et al., 2012) hence might not be sensitive
enough to detect changes. Therefore the use of alternate within
Fig. 2. (continued).
L. Herrington et al. / Physical Therapy in Sport 14 (2013) 188e198192
subject measurements for changes in such as knee circumference
(Jakobsen et al., 2010) have shown good reliability and a real clinical
change value of greater than 1 cm (Jakobsen et al., 2010) and hence
changes or differences in circumference of greater than 1 cm are
likely to be significant.
"Leg press limb symmetry index with less than 5% difference
Pre-operative quadriceps weakness (greater than 20% difference
between sides) has been shown to predict poor quadriceps strength
and low self-reported function after surgery (Adams et al., 2012;
Eitzen, Eitzen, Holm, Synder-Mackler, and Risberg, 2010).
"Normal gait walking and straight line jogging (8e10 min/mile)
Small deviations in normal gait patterns if not corrected have
the potential to become exaggerated when the patient starts to run
and return to more complex functional activities (Myer et al., 2008).
"Functional questionnaire score equal to or greater than
normative values
Patient derived subjective assessments of symptoms and func-
tion are often more robust when evaluating the outcome of ACLR
than clinical measurements such as arthrometers (Kocher,
Steadman, Briggs, Sterett, & Hawkins, 2004). The goal pre-
operatively for the athlete then would be to have functional
scores equal to or greater than that of the normal “non-athletic”
population. For the IKDC subjective questionnaire a score of greater
than 89% for males and 86% for females would exceed the reported
norm values (Anderson, Irrgang, Kocher, Mann, & Harrast, 2006;
Collins, Misra, Felson, Crossley, & Roos, 2011). Ideally, for the
KOOS questionnaire a score equal to or greater than normal values
for each of the following individual domains: pain 90e95%;
symptoms 84e91%, activities of daily living 92e98%, sport/recrea-
tion 80e91%, quality of life 80e90% (Collins et al., 2011;
Paradowski, Bergman, Sunden-Lundius, Lohmander, & Roos,
2006) would be required.
2.5. Post-op recovery phase
2.5.1. Aim
To overcome the effects of the operation, regain range of
movement and muscle activation, control effusion and achieve
normal walking gait.Typical rehabilitation activities
"Effusion control
"Muscle activation
"Range of movement
"Gait re-education
"Limb loadingTarget criteria to be achieved prior to progression
to the progressive limb loading activity phase
"Full quadriceps activation (SLR no lag $10 repetition)
"Range of movement 0e120
%
(minimum)
"Minimal effusion (<1 cm change at patella with activity and
diurnal variation)
"Bilateral squat to parallel (thighs relative to floor) with even
symmetrical weight bearing
"Gluteal muscle activation (undertake a bilateral short lever
bridge)
"Hamstring muscle activation (flex the knee in standing to 90
%
and undertake a bilateral straight leg bridge)
"Normal symmetrical gait
"Static cyclingRationale for targets to be achieved prior to pro-
gression to the progressive limb loading activity phase
"Full quadriceps activation (SLR with no lag through 10
repetitions)
Persistent quadriceps lag on SLR has been shown to indicate an
inability to actively fully extend the knee. If this is not achieved by
week 5 post-operation this would be considered a predisposing
factor for significant quadriceps weakness at 6 months post-oper-
ation (Potter & Foo, 2006). This activation failure of the quadriceps
is likely to serve as a major barrier to rehabilitation (Lynch et al.,
2012) limiting rehabilitation progress and increasing the risk of
developing patellofemoral pain (Myer et al., 2006).
"Range of movement with full extension and a minimum of 120
%
flexion
Early joint motion is beneficial when it comes to avoiding
capsular contractions, reducing swelling and pain, and early full
passive and active extensionwould appear to have no adverse effect
on knee laxity (Isberg et al., 2006). Even small losses of knee
extension (3e5
%
) appear to adversely affect subjective and objective
outcome markers later in the rehabilitation phase (Adams et al.,
2012). Establishing at least 120
%
of knee flexion allows the patient
to undertake static cycling the benefits of which are explained later.
Within the criteria establishing normal patella motion is also an
important component, because of its relationship to both loss of
flexion (Wilson, Press, Koh, Hendrix, & Zhang, 2009) and extension.
"Minimal effusion (<1 cm change at patella with activity)
As stated above changes in knee joint effusion are frequently
associated with irritation of intra-articular structures and articular
disorders in clinically active knees (Hurley, 1997) the level of effu-
sion being strongly associated with quadriceps inhibition, with
increasing effusion creating greater inhibition (Palmieri-Smith
et al., 2008). Pain and swelling should therefore be used to deter-
mine exercise progression (Potter & Foo, 2006) as it will relate to
the loading stresses which have been placed on the knee (Myer
et al., 2008). Measurement of knee circumference at the patella
has been shown to have strong intra-tester reliability and good
sensitivity to change (Jakobsen et al., 2010), thereforeit is suggested
that the impact of rehabilitation and activities of daily living is
monitored by changes in knee circumference. Jakobsen et al. (2010)
showed changes of greater than 1 cm to be clinically significant. In
practice the patient would measure knee circumference on first
rising and at the end of the day. The aim is that the measure should
not have changed by greater than 1 cm over the day. Greater
changes than this may be indicative of increasing joint effusion and
so joint stress, which may mean changing the loading the patient
undertakes to settle the irritation.
"Bilateral squat to parallel (thighs relative to floor) even sym-
metrical weight bearing
Neitzel, Kernozek, and Davies (2002) found that some ACLR
patient’s failed to symmetrically load their legs during squat up to
12 months post-op and this was related to poor functional
outcomes.
"Gluteal muscle activation
This is demonstrated by being able to undertake bilateral short
lever bridge exercise (10 repetitions to neutral hip extension).
Decreased gluteal muscle activity has been associated with
increased knee valgus during a variety of functional tasks (Zazulak
et al., 2007). Improvements in hip abduction and lateral rotation
L. Herrington et al. / Physical Therapy in Sport 14 (2013) 188e198 193
strength and activation have lead to the attainment of superior
neuromuscular alignment and control of the lower limb
(Khayambashi, Mohammadkhani, Ghaznavi, Lyle, & Powers, 2012;
Philippon et al., 2011).
"Hamstring muscle activation
This is demonstrated by flexing the knee in standing to 90
%
actively and being able to undertake a bilateral straight leg bridge
(heels on 30 cm high box) for 10 repetitionsto neutral hip extension.
Seto, Orofino, Morrissey, Medeiros, and Mason (1988) found
increased hamstring muscle activation and strength to be associated
with superior outcomes (functional scores and return to sport).
"Normal symmetrical gait
Abnormal gait patterns have been associated with quadriceps
weakness (Bush-Joseph et al., 2001), low patient satisfaction with
outcome after ACLR (Kocher et al., 2002), decreased functional
performance (Decker, Torry, Noonan, Sterett, & Steadman, 2004),
post-operative complications including osteoarthritis (Dye, Staubli,
Biedert, & Vaupel, 1999). Patients following ACLR have been shown
to have significantly different gait patterns 12 months post-oper-
ation (Hall, Stevermer, & Gillette, 2012) with these changes being
associated with articular cartilage matrix degeneration (Haughom
et al., 2012) and so osteoarthritis risk. The gait abnormalities also
often become further exaggerated when the patient returns to
running (Myer et al., 2008).
"Static cycling
Kutzner et al. (2012) found tibiofemoral joints shear stresses to
be considerably lower in cycling than walking. Low load cyclical
loading of articular surfaces promotes chrondrocyte activity
(Arokoski, Jurvelin, Vaatainen, & Helminen, 2000) and reduces the
potential compromise of articular cartilage during future loading
activities (Kviranta, Tammi, Jurvelin, Saamanen, & Helminen,1988).
The cycling should also aid in resolution of the often present bony
bruise reducing the risk of developing on going degenerative issues
within the joint (Davies-Tuck et al., 2010).
2.6. Progressive limb loading
2.6.1. Aim
Progressing the athlete from bilateral weight bearing activities
to full unilateral weight bearing activities in conjunction with being
able to undertake limited load acceptance activities (bilateral jump
landing and jogging). Together with progressing strength training
and work capacity of key lower limb muscles.Typical rehabilitation
activities
"Muscle strengthening and work capacity training
"Static movement dissociation
"Dynamic movement control (closed chain)
"Bilateral load acceptance
"Cardiovascular trainingTarget criteria to be achieved prior to
progression unilateral load acceptance activity
"Full range of movement
"Minimal activity related effusion (less than 1 cm change knee
circumference around the patella, diurnal variation)
"Maintain single-leg stance without significant postural sway at
5, 45 and 90
%
knee flexion (10 s hold) on a soft yielding surface.
"Star Excursion Balance Test (SEBT)
BAnterior and Posterior reach directions are symmetrical
BMedial and Lateral reach distance has less than a 10% dif-
ference in limb symmetry index (LSI)
BComposite score (total anterior, posterior, medial and
lateral) has less than 10% difference in LSI
"Single-leg squat to 90
%
(alignment control $10 repetitions;
QASLS score 0e1)
"Bilateral drop jump test [alignment control; QASLS score 0e1]
from 30 cm box
"Tuck jump test (score <3)
"Single-leg press 1.5$body weight (BW) (10 repetitions) e0e
90
%
knee flexion
"Gluteal muscle work capacity
BUnilateral short lever bridge on box (hip 45
%
)($25þeach leg
no greater than 5 repetition (rep) difference between sides)
"Hamstring muscle work capacity
BUnilateral long lever bridge on box (hip 45
%
)($25 þeach leg
no greater than 5 rep difference between sides)
"Calf muscle work capacity
BUnilateral heel raise ($25 þno greater 5 rep difference be-
tween sides)
"Function
BStraight line running (8e10 min/mile)
BStair ascent and descent (30 cm); alignment control sym-
metryRationale for the target criteria to be achieved prior to
progression unilateral load acceptance activity
"Full range of movement
The benefits of achieving full range of movement were dis-
cussed earlier, with respect of regaining full range of flexion this
also is indicative of an appropriately tracking patella and is asso-
ciated with a reduced risk of the development of patellofemoral
joint pain (Wilson et al., 2009). The regular monitoring of range of
movement for any significant change (>10
%
for flexion; >5
%
for
extension) may provide an early sign of the development of intra-
articular pathology such as arthrofibrosis (Shelbourne & Gray,
2009). Changes in range of movement may also reflect changes in
the level of joint effusion (Potter & Foo, 2006)
"Minimal activity related effusion (<1 cm change patella)
The impact of rehabilitation and activities of daily living is to be
continually monitored by change in knee circumference. Jakobsen
et al. (2010) showed changes of greater than 1 cm to be clinically sig-
nificant,indicatingthe levelsof load appliedwere causes of jointstress.
"Single-leg stance 5, 45 and 90
%
knee flexion (10 s hold) on
deformable pad
Multi angle static balance forms the pre-requisite to any dy-
namic activity (Myer et al., 2006), without good static balance
performance during dynamic tasks is likely to be significantly
compromised.
"Single-leg squat to 90
%
(alignment control $10 reps; QASLS
score 0e1)
"Bilateral drop jump test [QASLS score 0e1] from 30 cm box
"Tuck jump test (score <3)
Athletes who demonstrate symmetry in relation to limb align-
ment control during limb loading activities after ACLR may signif-
icantly reduce their potential for future ACL injury (Paterno et al.,
2010).
"Star Excursion Balance Test (SEBT)
During anterior reach of the SEBT there is a significant increase
in quadriceps EMG activity (Earl & Hertel, 2001) and the distance
L. Herrington et al. / Physical Therapy in Sport 14 (2013) 188e198194
has a moderate correlation to concentric strength (Thorpe &
Ebersole, 2008), symmetry of reach providing good indicator of
quadriceps function. The posterior reach direction generates
significantly greater hamstring muscle activity (Earl & Hertel, 2001)
and has a moderate correlation to concentric hamstring strength
(Thorpe & Ebersole, 2008), providing good indicator of hamstring
muscle function. Deficits in medial and lateral reach distances have
been associated with ACL deficient knees (Herrington, Hatcher,
Hatcher, & McNicholas, 2009) and furthermore both Fridén,
Zätterström, Lindstrand, and Moritz (1989) and Goldie, Bach, and
Evans (1989) reported increased postural sway (decreased stabil-
ity) in the medio-lateral direction to be significantly related to ACL
injury. Plisky, Rauh, Kaminski, and Underwood (2006) reported
deficits in composite reach distances of greater than 6% were
related to a significant increase in global lower limb injury risk.
"Single-leg press 1.5 BW (10rep) e0e90
%
knee flexion
A typical level of loading during a vertical jump landing is
around 1.5$body weight (Cleather, Goodwin, & Bull, 2013) in order
for progression to these activities it would be appropriate to have
force generation (and absorption) capabilities equal to those tasks.
"Gluteal muscle work capacity
As demonstrated by unilateral short lever bridge on box (hip
45
%
)($25 þeach leg no greater than 5 rep difference between
sides). Decreased gluteal muscle activity has been associated with
increased knee valgus during a variety of functional tasks (Zazulak
et al., 2007). This is further exaggerated when the muscles become
fatigued with repetitive loading (Herrington & McKenna, in press).
"Hamstring muscle work capacity
This is shown by achieving a unilateral long lever bridge on box
(hip 45
%
)($25 þeach leg no greater than 5 rep difference between
sides). Increased hamstring muscle activation and strength have
been associated with superior outcomes (functional scores and
return to sport) (Seto et al., 1988) increased work capacity is likely
to aid this relationship further.
"Calf muscle work capacity
As demonstrated by unilateral heel raise (>25 reps and no
greater 5 rep difference between sides). Schlumberger (2002) re-
ported an average of an 8% strengthdeficit in calf muscle strength 6
months following ACLR. Lack of strength in this muscle group is
likely to affect both load absorption and propulsion significantly
during running gait.
"Function
BStraight line running (8e10 min/mile)
BStair ascent and descent (30 cm); alignment control sym-
metry (QASLS score 0e1)
Roewer, Di Stasi, and Snyder-Mackler (2011) found reduced peak
extensor moments and reduced knee flexion angle during walking
at 6 months post-operation, with peak knee extensor moment and
peak knee power absorption significantly less in involved knee at
both 6 and 24 months post-operation, despite having symmetri-
cally equal quadriceps strength at 6 months post-operation. They
concluded that abnormal movement strategies during gait can still
be present 2 years post-op despite symmetrical quads strength, it
then becomes important to specifically assess walking and running
gait along with functional activities such as stair ascent and
descent, to address any abnormalities which could otherwise
persist for a prolonged period.
2.7. Unilateral load acceptance activity
2.7.1. Aim
Progressing athlete from bilateral load acceptance activities to
full unilateral load acceptance activities in multiple planes of
movement. Alongside progressing strength and force development
training and work capacity of key lower limb muscles.Typical
rehabilitation activities
"Muscle strengthening and work capacity training
"Unilateral load acceptance activities in multiple planes and
reactive landings situations
"Bilateral multi-plane and unilateral single plane plyometric
activitiesTarget criteria to be achieved prior to progression to
sport specific task training activities
"SEBT symmetry and within norms
"Single-leg hop landing (alignment control; QASLS score 0e1)
BSingle-leg hop for distance (LSI for distance <5%)
BForward and side hop from 30 cm box
"Tuck jump test (score 0e1)
"Cross over hop LSI <5%
"Lower limb closed chain strength
B10 RM Single-leg press >2.0 BW e0e90
%
knee flexion
B10 repetition unilateral leg press to 90
%
within 5% of
contralateral leg
BOverall weight lifted <10% down on pre-injury level 3e6 RM
of squat and deadlift.
"Isolated (open chain) quadriceps and hamstring strength
BIsokinetic extensors total work >300%BW
BIsokinetic flexor eccentric peak torque >130% of concentric
flexor peak torque
BNo breaks in extensor or flexor isokinetic curve during
testing
"Rate of force development; vertical hop test LSI <5%Rationale
for target criteria to be achieved prior to progression to sport
specific task training activities
"SEBT symmetry and at upper end of normal values
As there is only a weak association between static balancee
stability activities and ability to dissociate movement (Riemann &
Schmitz, 2012) it is important that patients have symmetrical and
normal movement dissociation skills, not only to allow unrestricted
movement but also as a decreased performance is associated with
reduced injury risk (Plisky et al., 2006).
"Single-leg (hop) land (alignment control; QASLS score 0e1)
BSingle-leg hop for distance (LSI for distance <5%)
BForward and side hop from 30 cm box
BTuck jump test (score 0e1)
Athletes who demonstrate symmetry in relation to limb align-
ment control during limb loading activities after ACLR may signif-
icantly reduce their potential for future ACL injury (Paterno et al.,
2010).
"Cross over hop LSI <5%
There is a strong relationship between cross over hop perfor-
mance and functional outcome (Trulsson, Roos, Ageberg, &
Garwicz, 2010) correlating significantly to IKDC subjective and
KOOS questionnaire scores (Reinke et al., 2011). The work of Munro
and Herrington (2011) showed LSI needs to be in excess of 90% to be
deemed normal.
L. Herrington et al. / Physical Therapy in Sport 14 (2013) 188e198 195
"Lower limb closed chain strength
B10 RM Single-leg press >2.0 BW e0e90
%
knee ROM
B10 rep unilateral leg press to 90
%
within 5% of contralateral
leg
BOverall weight lifted <10% down on pre-injury level 3e6 RM
of squat and deadlift.
"Isolated (open chain) quadriceps and hamstring strength
BIsokinetic extensors total work >300%BW (60
%
/s concentric)
BIsokinetic flexor eccentric peak torque >120e130% of
concentric flexor peak torque (60
%
/s)
BNo breaks in extensor or flexor isokinetic curve during
testing (60
%
/s)
Lewek, Rudolph, Axe, and Snyder-Mackler (2002) compared
post ACLR strong group (>90%LSI) weak group (<90%LSI) and
found strength to have a significant effect on early stance phase
knee angles and moments and quadriceps strength during walking
and jogging, showing strength plays significant role in functional
performance (Schmitt et al., 2012). Breaks within the isokinetic
knee extensor torque curve have been shown to be associated with
patellofemoral pain (Anderson & Herrington, 2003) and even
osteochondral lesions of the patellofemoral joint (Herrington,
Williams, & George, 2003) and are likely to be related to quadri-
ceps inhibition (Dvir, Halperin, Shaklar, & Robinson, 1991), which
will need to be overcome prior to successful return to full unre-
stricted activity. Similarly, breaks within the flexor curve have been
associated with poor functional scores in ACL deficient patients
(Herrington, Turner, & Horsley, 2003).
"Rate of force development; vertical hop test LSI <5%
Both Angelozzi et al. (2012) and Myer et al. (2012) showed
significant deficits in rate of force development in patients post
ACLR which had an impact of functional performance and obviously
will affect the ability to performance sport specific speed and agility
based tasks.
2.8. Sport specific task training activities
2.8.1. Aim
Improving athlete’s work capacity in the ability to undertake
unilateral load acceptance activities in multiple planes of move-
ment with a reactive random element. Develop athlete’s ability to
carry out specific multi-directional running and landing tasks
which are aligned to needs of their sport, along with any other sport
skill based tasks.Typical rehabilitation activities
"Muscle strengthening and work capacity training
"Unilateral load acceptance activities in multiple planes and
reactive landings situations (with fatigue element)
"Sports specific aligned running agility tasks
"Sports specific aligned skill tasksTarget criteria to be achieved
prior to progression to unrestricted sport specific training
"Limb alignment control following fatiguing task
BSEBT symmetry and within norms
BSingle-leg (hop) land (alignment control; QASLS score 0e1)
-
Single-leg hop for distance (LSI <5%, and <5% pre-op
score)
-
Forward and side hop from 30 cm box (alignment
control; QASLS score 0e1)
"Running speed
BAflying run (10 m) through Optojump system and speed
gates, with outcome measures of L v R side symmetry of
contact and flight times within 5e10%
BAgility run time symmetrical (modified T or alternate sport
specific) <10% pre-op time
"Function
BSport specific tasks with alignment control under random
practice and fatigue scenarios (video analysis of alignment
control; QASLS score 0e1)Rationale for the target criteria to
be achieved prior to progression to unrestricted sport specific
training
BLimb alignment control following fatiguing task (sport specific
intensity-duration)
"SEBT symmetry and within norms
"Single-leg (hop) land (alignment control; QASLS score 0e1)
-
Single-leg hop for distance (LSI <5%, and <5% pre-op
score)
-
Forward and side hop from 30 cm box (alignment
control; QASLS score 0e1)
Fatigue has been shown to have a significant effect on limb
alignment control during a variety of loading tasks (Herrington &
McKenna, in press; Khayambashi et al., 2012) the athlete is ex-
pected to show near perfect control after a fatiguing activity.
"Running speed
BAflying run (10 m) through Optojump system and speed
gates, with outcome measures of L versus R side symmetry
of contact and flight times within 5e10%
BAgility run time symmetrical (modified T or alternate sport
specific) <10% pre-op time
"Function
BSport specific tasks with alignment control under random
practice and fatigue scenarios (video analysis of alignment
control; QASLS score 0e1)
To more appropriately reflect motor learning practices appro-
priate neuromuscular control needs to be undertaken whilst car-
rying out tasks of progressively increasing complexity, where more
open skill elements become incorporated in a more and more
random fashion, once the closed skill tasks have been mastered
(McCormick, 2012; Verstegen, Falsone, Orr, & Smith, 2012). The
athlete needs to be able to demonstrate transference of the
neuromuscular control strategy into the “real world”.
3. Discussion
Barber-Westin and Noyes (2011) in their review of return to sport
criteria following ACLR noted only 13% of the studies reported any
criteriafor returningthe athlete tosport. These criteria includemuscle
strength or thigh circumference (28 studies), general knee examina-
tion (15 studies), single-leg hop tests (10 studies), Lachman rating
(one study) and validated questionnaires (one study). All of these
criteria would seem insufficient when compared to the loading
stresses the knee is exposed to during normal sporting activities. This
clinical commentary has attempt to produce a progressive series of
targets for the athlete following ACLR with the goal of gradually
increasing the stress the athlete and theirknee are exposed to, in order
to develop the robustness required to return to sport.
Conflict of Interest
The authors have no conflicts of interest related to this paper.
Ethical Approval
The study was literature based and no ethical approval was sort.
Funding
None declared.
L. Herrington et al. / Physical Therapy in Sport 14 (2013) 188e198196
Acknowledgments
The authors wish to acknowledge the role of the following
people in developing the consensus: Raph Brandon (English Insti-
tute of Sport); Chris Price (English Institute of Sport); Simon
Spencer (English Institute of Sport); Ashleigh Wallace (English
Institute of Sport and British Olympic Association); Lindy Hardy
(Scottish Institute of Sport); Phillip Glasgow (Northern Ireland
Institute of Sport) and thank them for their work in the consensus
development.
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