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Incidence and prevalence of patellofemoral pain: A systematic review and meta-analysis

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Background Patellofemoral pain is considered one of the most common forms of knee pain, affecting adults, adolescents, and physically active populations. Inconsistencies in reported incidence and prevalence exist and in relation to the allocation of healthcare and research funding, there is a clear need to accurately understand the epidemiology of patellofemoral pain. Methods An electronic database search was conducted, as well as grey literature databases, from inception to June 2017. Two authors independently selected studies, extracted data and appraised methodological quality. If heterogeneous, data were analysed descriptively. Where studies were homogeneous, data were pooled through a meta-analysis. Results 23 studies were included. Annual prevalence for patellofemoral pain in the general population was reported as 22.7%, and adolescents as 28.9%. Incidence rates in military recruits ranged from 9.7–571.4/1,000 person-years, amateur runners in the general population at 1080.5/1,000 person-years and adolescents amateur athletes 5.1%–14.9% over 1 season. One study reported point prevalence within military populations as 13.5%. The pooled estimate for point prevalence in adolescents was 7.2% (95% Confidence Interval: 6.3%–8.3%), and in female only adolescent athletes was 22.7% (95% Confidence Interval 17.4%–28.0%). Conclusion This review demonstrates high incidence and prevalence levels for patellofemoral pain. Within the context of this, and poor long term prognosis and high disability levels, PFP should be an urgent research priority. PROSPERO registration CRD42016038870
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RESEARCH ARTICLE
Incidence and prevalence of patellofemoral
pain: A systematic review and meta-analysis
Benjamin E. Smith
1,2
*, James Selfe
3
, Damian Thacker
4
, Paul Hendrick
5
,
Marcus Bateman
1
, Fiona Moffatt
5
, Michael Skovdal Rathleff
6,7
, Toby O. Smith
8
, Pip Logan
2
1Derby Teaching Hospitals NHS Foundation Trust, London Road Community Hospital, Derby, United
Kingdom, 2Division of Rehabilitation and Ageing, School of Medicine, University of Nottingham, Nottingham,
United Kingdom, 3Department of Health Professions, Manchester Metropolitan University, Manchester,
United Kingdom, 4PhysioWorks (Sheffield), Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield,
United Kingdom, 5Division of Physiotherapy and Rehabilitation Sciences, School of Health Sciences,
University of Nottingham, Nottingham University Hospitals (City Campus), Nottingham, United Kingdom,
6Research Unit for General Practice in Aalborg, Department of Clinical Medicine at Aalborg University,
Aalborg, Denmark, 7Department of Occupational Therapy and Physiotherapy, Department of Clinical
Medicine, Aalborg University Hospital, Aalborg, Denmark, 8Nuffield Department of Orthopaedics,
Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
*benjamin.smith3@nhs.net
Abstract
Background
Patellofemoral pain is considered one of the most common forms of knee pain, affecting
adults, adolescents, and physically active populations. Inconsistencies in reported
incidence and prevalence exist and in relation to the allocation of healthcare and research
funding, there is a clear need to accurately understand the epidemiology of patellofemoral
pain.
Methods
An electronic database search was conducted, as well as grey literature databases, from
inception to June 2017. Two authors independently selected studies, extracted data and
appraised methodological quality. If heterogeneous, data were analysed descriptively.
Where studies were homogeneous, data were pooled through a meta-analysis.
Results
23 studies were included. Annual prevalence for patellofemoral pain in the general popula-
tion was reported as 22.7%, and adolescents as 28.9%. Incidence rates in military recruits
ranged from 9.7–571.4/1,000 person-years, amateur runners in the general population at
1080.5/1,000 person-years and adolescents amateur athletes 5.1%–14.9% over 1 season.
One study reported point prevalence within military populations as 13.5%.
The pooled estimate for point prevalence in adolescents was 7.2% (95% Confidence
Interval: 6.3%–8.3%), and in female only adolescent athletes was 22.7% (95% Confidence
Interval 17.4%–28.0%).
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 1 / 18
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OPEN ACCESS
Citation: Smith BE, Selfe J, Thacker D, Hendrick P,
Bateman M, Moffatt F, et al. (2018) Incidence and
prevalence of patellofemoral pain: A systematic
review and meta-analysis. PLoS ONE 13(1):
e0190892. https://doi.org/10.1371/journal.
pone.0190892
Editor: Hazel RC Screen, Queen Mary University of
London, UNITED KINGDOM
Received: October 12, 2017
Accepted: December 21, 2017
Published: January 11, 2018
Copyright: ©2018 Smith et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the paper.
Funding: This report is independent research
arising from a Clinical Doctoral Research
Fellowship, Benjamin E Smith, ICA-CDRF-2015-01-
002 supported by the National Institute for Health
Research (NIHR) and Health Education England
(HEE). The views expressed in this publication are
those of the authors and not necessarily those of
the NHS, the NIHR, HEE or the Department of
Health.
Conclusion
This review demonstrates high incidence and prevalence levels for patellofemoral pain.
Within the context of this, and poor long term prognosis and high disability levels, PFP
should be an urgent research priority.
PROSPERO registration
CRD42016038870
Introduction
There are over 100,000 primary care appointments a day in the United Kingdom (UK) for
musculoskeletal (MSK) pain disorders [1], with an associated £7.4 billion cost annually to the
UK economy through absenteeism [2]. In the United States an estimated 126.6 million Ameri-
cans suffer from a musculoskeletal disorder, putting a burden onto the economy with an esti-
mated cost of $213 billion annually through healthcare costs and sickness absence [3]. Knee
pain is the second most prevalent condition, with patellofemoral pain (PFP) being considered
one of the most common forms of knee pain [4], with a prevalence cited between 15% to 45%
[5]. It is described as non-traumatic in nature, with diffuse anterior knee pain on activities that
load the joint such as squatting, running, climbing and descending stairs [4].
Variations in reported incidence and prevalence may be due to differing populations
assessed, inconsistencies in the diagnosis and lack of high quality evidence on which to base
assessment [6,7]. PFP is thought to affect the general population [8], and more specifically
adolescents [9], young active adults [10], elite athletes [11,12], and military recruits [13];
with higher incidence and prevalence rates often cited among females [13,14]. There is no
definitive gold standard method to clinically diagnose PFP [15]. Diagnosis has historically
been based on detailed subjective and objective assessments, with pain on a number of special
tests including the patellofemoral compression test, palpation of the patella and pain of resisted
knee extension [13,1618]. It is likely that this method of diagnosis could under-estimate the
true incidence or prevalence rates, since many people with PFP reduce or withdraw from their
aggravating activity [19], and consequently pain on palpation may only identify those with
higher levels of pain, or still participating in activities. Alternatively, due to high sensitivity of
historical tests, it may be that this approach results in an over-estimation instead [20]. Recently
PFP has been re-defined as: self-reported pain around or behind the patella aggravated by
activities that loads the joint, e.g. squats, stairs, running or jumping; with special tests and pain
on prolonged rest additional but not essential [4].
To date, no systematic reviews have been published on the incidence and prevalence for
PFP; with publications often employing an indirect course of secondary and even tertiary
referencing when citing incidence or prevalence data for PFP [7]. In relation to clinical deci-
sion-making, and the allocation of healthcare and research funding, there is a clear need to
accurately understand the epidemiology of this problem. Therefore, in the context of the cur-
rent uncertainty regarding PFP, this systematic review synthesises epidemiological data using
a contemporary case definition and clear population classifications [4], to gain an understand-
ing of incidence and prevalence data for this condition.
Method
This systematic review followed the recommendations of the meta-analyses in observational
studies (MOOSE) guidance statement [21], the recommendations of the PRISMA statement
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 2 / 18
Competing interests: The authors have declared
that no competing interests exist.
where relevant [22], and was registered with the International Prospective Register of System-
atic Reviews (PROSPERO reference CRD42016038870).
Data sources and search strategy
An electronic database search was conducted on titles and abstracts from inception to June
2017 using the following databases: Medline via PubMed, EMBASE, the Cumulative Index to
Nursing and Allied Health Literature (CINAHL), and Web of Science. For the keywords
search strategy used see Table 1. The database searches were accompanied by hand searches of
the reference list of included articles, as well as contacting authors for all included and poten-
tially included studies. The grey literature and ongoing studies were searched using the follow-
ing databases: OpenGrey, WHO International Clinical Trials Registry Platform, ClinicalTrials.
gov and the NIHR portfolio.
Inclusion criteria included study population of any age and any setting with signs and
symptoms of PFP, defined as; anterior or retropatellar pain reported on at least two of the fol-
lowing activities; prolonged sitting, ascending or descending stairs, squatting, jumping and
running [4]. There was no restriction on the type of setting for potential included papers.
Exclusion criteria included: if the study population was selected from a specific disease area
(e.g. diabetes, rheumatoid arthritis, osteoarthritis); if the study population comprised of partic-
ipants with other knee pathology (e.g. knee ligamentous instability, history of patella disloca-
tions, true knee locking or giving way, patella or iliotibial tract tendinopathy, osteoarthritis).
Included studies were required to report incidence or prevalence data, and had to be pub-
lished in English or where an English translation was available.
Study selection
One reviewer (BES) undertook the searches. Titles and abstracts were screened by one
reviewer (BES), with potential eligible papers retrieved and independently screened by two
reviewers (BES & JS). Initial inclusion agreement was 83%. Five disagreements were due to
case definition [9,12,2325], and were discussed and resolved through consensus. Seven fur-
ther case definition disagreements not resolved through consensus were resolved through a
third reviewer (PH) [2632].
Data extraction
One reviewer (BES) extracted data relating to study design, population and setting, case defini-
tion, incidence and prevalence data, which was independently verified by a second reviewer
(DT).
Quality appraisal
In the absence of any validated quality assessment tools [33], two reviewers (BES & JS) inde-
pendently appraised methodological quality using a tool developed by Hayden et al. [34] for
the evaluation of the quality of prognostic studies in systematic reviews, and adapted by Luime
Table 1. Search strategy.
Search Term
1”anterior knee pain” or “AKP” or “patellofemoral pain syndrome” or “PFPS” or “patellofemoral pain” or “PFP”
2Inciden$ or prevalen$ or cohort$ or prospective or epidemiolog$ or trial
31 and 2 limited to English language
https://doi.org/10.1371/journal.pone.0190892.t001
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 3 / 18
et al. [35] for evaluation of the quality of epidemiological studies in systematic reviews. This
assessed appropriateness and reporting of: the study population, case definition, and the
response rate and follow-up of the cohort. To be judged as ‘high quality’, all three criteria had
to be met; with male and females represented, a clear reproducible case definition relevant to
our inclusion criteria and a response rate above 75%. Percentage agreement between the two
reviewers was 94%, all disagreements were discussed and resolved through consensus.
Data synthesis
Study heterogeneity was assessed through visual examination of the data extraction table on
details related to participant characteristics, case definition, study design and process of the
included studies. If heterogeneous, data were analysed narratively to assess trends in preva-
lence and incidence across the studies. When data allowed, incidence rates were converted to
cases per 1,000 person-years, with associated 95% confidence intervals (CI) [36]. Where stud-
ies were homogeneous, data were pooled through a meta-analysis. Statistical heterogeneity was
assessed using the I
2
statistic where 0% to 25% was low, 26% to 74% moderate and 75% and
over high statistical heterogeneity [37]. When outcomes presented with low statistical hetero-
geneity, data were pooled using a fixed-effects model, with moderate or high statistical hetero-
geneity a random-effects model was adopted. All data analyses were performed using Stata
version 14.0 (College Station, TX, USA) [38].
Results
Study selection
The search results are presented in Fig 1. From a total of 7,746 titles 66 papers were potentially
eligible. One unpublished trial was identified, however the author declined to share the details.
43 full-text articles were excluded; 37 due to case definition not meeting criteria [10,25,39
73], three due to no prevalence or incidence data being recorded [23,74,75], and two because
they were a replication of another included study [76,77]. In one study participants were
tested longitudinally over multiple years, with participants being eligible to enrol multiple
times, and therefore was excluded [78]. 23 studies met the eligibility criteria and were included
in the final review, 12 reporting incidence data [13,1618,26,28,30,32,7982], and 13 reporting
prevalence data [5,9,1113,16,24,27,29,31,8385]. Of the included 23 papers, 12 authors
were contacted for clarification on: raw data extraction [11,26,28,29,79,80,84], and participant
information [5,12,13,18,31]. Eight responded and gave further details, where available
[5,12,13,28,29,31,80,84]. The authors that were uncontactable, or did not have available infor-
mation account for the ‘unknown’ items in the characteristics table.
Study characteristics
A summary of the main characteristics of the included studies, with the main results can be
found in Tables 2and 3for incidence and prevalence respectively. Six papers within the mili-
tary setting (n= 4,199) reported incidence data [13,17,32,7981], two papers reported inci-
dence data within the general adult population setting (n= 140) [26,82], and four papers
reported incidence data within the general adolescent population (n= 985) [16,18,28,30].
One paper within the military setting (n= 1,525) reported prevalence data [13], three papers
reported prevalence data within the general adult population setting (n= 1,1011) [5,24,83],
six papers reported prevalence data the general adolescent population setting (n= 5,090)
[9,16,27,29,31,84], and three papers reported prevalence data the elite athlete setting (n= 568)
[11,12,85].
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 4 / 18
As a result of study heterogeneity, with the exception of five studies that reported preva-
lence data in the adolescent population, a narrative synthesis was conducted.
Quality appraisal
The results of the methodological quality appraisal can be found in Table 4. 43.5% (10/23) of
the included studies were high quality (quality score = 3/3), according to our definition. 26.1%
(6/23) recorded a quality score of 2/3, and seven studies (30.4%) recorded a score of 1/3. The
main risk of bias and low methodological quality was due to ten studies having populations
comprising only male or female participants, and one study not describing the participant’s
sex [11,1618,26,2931,80,82,85]. Three studies had a response rate of below 75% [18,27,28];
two had an unknown response rate [11,85]; and four studies had imprecise case definitions
[17,27,30,31]; all were scored low accordingly.
Military
Incidence. Five studies reported incidence rates for military recruits, with a predomi-
nantly male population, that ranged from 9.7–571.4 cases per 1,000 person-years [17,32,79
81]. One study, with a mixed female and male military population, reported an incidence rate
of 22 cases per 1,000 person-years, with female recruits being reported as 33 and males as 15,
cases per 1,000 person-years [13].
Prevalence. One study with a mixed female and male military recruit population reported
a point prevalence of 13.5%, females 15.3% and males 12.3% [13].
General adult population
Incidence. One study with novice recreational female runners recorded a 10-week inci-
dence rate of 1080.5 cases per 1,000 person-years [82]. One study with female amateur colle-
giate athletes (mean age 19.4) reported an athletic season incidence rate of 1.9%.
Fig 1. PRISMA 2009 flow diagram.
https://doi.org/10.1371/journal.pone.0190892.g001
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 5 / 18
Table 2. Incidence.
Study Quality
score
Study population Sample
Size
Case definition Response
rate
Results
Military
Boling
(2010) [13]
3/3 United States Naval
Academy (USNA) (39.8%
female; mean age unknown,
range 18–25).
1,525 Retropatellar pain of any duration with two
of the following activities: ascending/
descending stairs, hopping/jogging,
prolonged sitting with flexed knees,
kneeling, and squatting. Plus one of the
following: pain on palpation of medial or
lateral patellar facets, or pain on palpation
of the anterior portion of the medial or
lateral femoral condyles.
1,319/1,525
(86.5%)
22/1,000 person-years (95% CI: 15/
1,000, 29/1,000 person-years). Female
incidence was 33/1,000 person-years
(95% CI: 20/1,000, 45/1,000 person-
years) and in males was 15/1,000
person-years (95% CI: 7/1,000, 22/
1,000 person-years).
Coppack
(2011) [79]
2/3 British Army recruits,
United Kingdom (27.9%
female, mean age 19.6).
743 Pain from at least 2 of the following:
prolonged sitting, stair climbing, squatting,
running, kneeling, and hopping/jumping;
insidious onset of symptoms unrelated to a
traumatic incident; and presence of pain on
palpation of the patellar facets, on step
down from a 25-cm step, or during a
double-legged squat.
743/743
(100%)
14 week incidence 36 / 743 (4.8%; 95%
CI, 3.5–6.7). 180/1,000 person-years
(95% CI: 127.9/1,000, 246.5/1,000
person-years).
Kaufman
(1999) [80]
2/3 United States Navy Recruits.
(100% male; mean age 22.5
years)
449 Ill-defined ache of insidious onset localized
to the peripatellar area, plus pain on
palpation of patella and peripatellar soft
tissues.
449/449
(100%)
25 week incidence 35/449 (7.8%).
162.1/1,000 person-years (95% CI:
114.7/1,000, 223.0/1,000 person-years).
Milgrom
(1991) [17]
1/3 Infantry recruits, Israel
(100% male; age unknown).
390 Subjective complaint of anterior knee pain,
non-traumatic, with objective finding of
pain on patellofemoral compression test
and palpation of patella borders.
390/390
(100%)
14 week incidence 60/390 (15.4%).
571.4/1,000 person-years (95% CI:
439.9/1,000, 730.5/1,000 person-years).
Thijs (2007)
[32]
3/3 Belgian Royal Military
Academy recruits (22.6%
female; mean age 19).
84 Two of the following: pain on direct
compression of the patella with the knee in
full extension, tenderness of the posterior
surface of the patella on palpation, pain on
resisted knee extension, or pain with
isometric quadriceps muscle contraction.
84/105
(80%)
6 week incidence 36/84 (42.9%). 9.7/
1,000 person-years (95% CI: 6.9/1,000,
13.3/1000 person-years).
Wills (2004)
[81]
3/3 British Army Recruits
(95.2% male; median age
19.4)
1,008 Pain around the anterior aspect of the knee,
insidious onset and no evidence of trauma
926/1,008
(91.9%)
12 week incidence 81/926 (8.7%).
379.1/1,000 person-years (95% CI:
303.0/1,000, 468.7/1,000 person-years).
General Adult Population
Devan
(2004) [26]
2/3 Female amateur collegiate
hockey, basketball and
athletic athletes, USA (mean
age 19.4).
63 Pain in or under patella while running,
going up or down stairs; with diffuse pain
on palpation.
53/63
(84.1%)
1 athletic season incidence 1/53
(1.9%).
Thijs (2011)
[82]
2/3 Female novice recreational
runners on a 10 week start
to run programme, Belgium
(mean age 38.4)
77 Retropatellar pain during and/or after
activities such as running, squatting,
kneeling, going up and down stairs, cycling,
prolonged sitting with the knee in flexion,
or rising from a seated position. And 2 of
the following: pain while compressing the
patella, tenderness of patella on palpation,
painful resisted knee extension and pain
when isometrically contracting the
quadriceps 15˚ flexion.
77/77
(100%)
10 week incidence 16/77 (20.8%).
1080.5/1,000 person-years (95% CI:
639.6/1,000, 1717.0/1,000 person-
years).
General Adolescents Population
Finnoff
(2011) [28]
2/3 High School runners aged
14–18, USA (45.9% female;
mean age 16)
98 Anterior knee pain that was exacerbated by
deep knee bending and/or climbing stairs
plus pain on one of the following: (1)
pressure over the subject’s distal quadriceps
tendon combined with active contraction of
his or her quadriceps muscle (patellar grind
test) or (2) direct palpation of the medial or
lateral patellar facets.
98/1500
(6.5%)
1 running season incidence 5/98
(5.1%).
(Continued)
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 6 / 18
Prevalence. Annual prevalence in the general population was reported as 22.7%, with the
annual prevalence in females 29.2% and males 15.5% [83]. Point prevalence in females was
reported as 12% to 13% [5]. Point prevalence during a multi-day amateur cycling event for
mixed male and female was reported as 35% [24].
General adolescents population
Incidence. Two studies recorded the incidence rate over one season for female adolescent
athletes as 9.7%–14.9%, or 0.97–1.09 per 1,000 athletic exposures [16,30], and one study
recorded the incidence rate over two seasons with adolescents participating in physical educa-
tion (sex unknown) as 42.6 cases per 1,000 person-years [18]. One mixed sex study of high
school runners reported the incidence rate over one running season as 5.1% [28].
Prevalence. Two studies reporting point prevalence (Molgaard [9] and Rathleff [84]) on
mixed male and female adolescents were deemed suitably homogenous, and accordingly were
pooled in a meta-analysis. Statistical heterogeneity was negligible (I
2
= 5.4%), and the pooled
estimate of point prevalence using a fixed effects model was 7.2% (95% CI 6.2%–8.3%). Point
prevalence in female only adolescents was reported as 16.3% [16].
Three studies reporting point prevalence (Hall [29], Myer [16], and Steinberg [31]) on
female only adolescent athletes were deemed suitably homogenous, and accordingly were also
pooled in a meta-analysis. Statistical heterogeneity was high (I
2
= 85.7%), and the pooled esti-
mate of point prevalence using a random effects model was 22.7% (95% CI 17.4%–28.0%).
One study if mixed sex adolescent reported an annual prevalence of 28.9% [27].
Elite athletes
Prevalence. One study with professional male cyclists reported an annual prevalence of
35.7% with symptoms of any duration, and 6.4% with symptoms lasting greater than 30 days
[12]. One study of female athletes (mean age 21.6) at the 3rd Iranian Sports Olympiad reported
point prevalence of symptoms greater than 3 months of 16.7% [11]; and another with female
university ballet dancers reported point prevalence (of unknown duration) as 29.3% [85].
Table 2. (Continued)
Study Quality
score
Study population Sample
Size
Case definition Response
rate
Results
Herbst
(2015) [30]
1/3 Female adolescent
basketball players in middle
and high school, USA (mean
age 12.7 years).
255 Anterior Knee Pain Scale score <100;
International Knee Documentation
Committee (IKDC) form, standardized
history and physician-administered
physical examination.
255/329
(77.5%)
1 season incidence 38/255 (14.9%).
0.97 per 1,000 athletic exposures (1
game or training session).
Myer (2010)
[16]
2/3 Female adolescent athletes
in middle and high school,
USA (mean age 13.4 years)
152 Anterior Knee Pain Scale score <100; knee
pain with or shortly following activity and
also if anterior knee tenderness was recent.
145/152
(95.4%)
1 season incidence 14/145 (9.7%). 1.09
per 1,000 athletic exposures (1 game or
training session).
Witvrouw
(2000) [18]
1/3 Students taking physical
education, aged 17–21 in
Belgium (sex unknown;
mean age 18.6)
480 Retropatellar pain >6 weeks during
physical activities such as jumping,
running, squatting, and going up or down
stairs. Plus two of the following; pain on
direct compression of the patella,
tenderness of the posterior surface of the
patella, pain on resisted knee extension, and
pain with isometric quadriceps contraction.
282/480
(58.8%)
2 year incidence 24/282 (8.5%). 42.6/
1,000 person-years (95% CI: 27.9/
1,000, 62.4/1,000 person-years).
Female incidence was 13/131 (9.9%),
49.6/1,000 person-years (95% CI: 27.6/
1,000, 82.7/1,000 person-years); male
was 11/151 (7.3%), 36.4/1,000 person-
years (96% CI: 19.2/1,000, 63.3/1,000
person-years).
Information not within publication, authors contacted for clarification.
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Incidence and prevalence of patellofemoral pain
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Table 3. Prevalence.
Study Quality
score
Study population Sample
Size
Case definition Response
rate
Results
Military
Boling
(2010) [13]
3/3 United States Naval Academy
(USNA) (39.8% female; mean age
unknown, range 18–25).
1,525 Retropatellar pain of any duration with two
of the following activities: ascending/
descending stairs, hopping/jogging,
prolonged sitting with flexed knees,
kneeling, and squatting. Plus one of the
following: pain on palpation of medial or
lateral patellar facets, or pain on palpation of
the anterior portion of the medial or lateral
femoral condyles.
1,525/1,525
(100%)
Point prevalence of PFPS was 13.5%
(95% confidence interval (CI): 11.7%,
15.3%]. For females and males it was
15.3% (95% CI: 13.7%, 16.9%) and 12.3%
(95% CI: 11.1%, 13.4%), respectively.
General Adult Population
Dey (2016)
[83]
3/3 Community within the UK.
Convenience sample of attendance
at a University science fair (53%
female; mean age 30).
111 Anterior knee or retropatellar pain, often
bilateral, of insidious onset present for at
least a month and associated with pain or
difficulty with prolonged sitting or activities
which load the patellofemoral joint, e.g.,
ascending or descending stairs, running and
squatting. Positive diagnosis identified
through a self-report questionnaire
(SNAPPS- Survey instrument for Natural
history, Aetiology and Prevalence of
Patellofemoral pain Studies)
110/111
(99%)
Annual prevalence 25/110 (22.7%).
Females 67%; males 33%.
Roush
(2012) [5]
3/3 18–35 year old females, general
population, USA (mean age 24.7)
769 Anterior Knee Pain Scale score <83 724/769
(94.1%)
Point prevalence was 12–13%.
Weiss
(1985) [24]
3/3 Amateur multi-day cyclist in USA
(69% male; mean age 41.4).
132 Self-reported complaint of patella pain
during a cycling event. Tenderness of
posterior aspect of patella during flexion and
extension.
113/132
(86%)
Point prevalence was 35%.
General Adolescents Population
Fairbank
(1984) [27]
1/3 13–17 year-old students, randomly
selected from a comprehensive
school in the United Kingdom
(49% female, mean age 14.7)
446 11 point questionnaire, including: Do you
like playing sport? Have you had painful
knees in the last year? Do your knees hurt
climbing stairs? Do your knees hurt coming
downstairs? Where do you feel the pain in
your knees? Does your knee hurt after sitting
for a long time? Does your knee hurt only
after a lot of exercise?
446/1850
(24.1%)
Annual prevalence 129/446 (28.9%).
Hall (2015)
[29]
2/3 Female adolescent athletes in
middle and high school, USA
(mean age 14.0).
546Assessment included the Anterior Knee Pain
Scale (AKPS), International Knee
Documentation Committee (IKDC) form,
standardized history and physician-
administered physical examination.
546/546Point prevalence 151/546(28%).
Molgaard
(2011) [9]
3/3 16–18 year-old students at one
local high school in Denmark
(mixed sex; mean age 16.9)
299 Anterior knee pain during physical activity
for at least 1 month and pain in at least two
of the following four tests: isometric
contraction of quads, concentric extension
against resistance, palpation of joint line,
and compression of the patella.
227/299
(76%)
Point prevalence 13/227 (5.7%). Females
69%; males 31%.
Myer
(2010) [16]
2/3 Female adolescent athletes in
middle and high school, USA
(mean age 13.4 years).
240 Anterior Knee Pain Scale score <100; knee
pain with or shortly following activity and
also if anterior knee tenderness was recent.
240/240
(100%)
Point prevalence was 39/240 (16.3%).
Rathleff
(2014) [84]
3/3 Population-based cohort of
students from secondary schools,
Denmark, aged 15–19 years (64.9%
female; mean age 17.2).
2,200 Insidious onset of anterior knee or
retropatellar pain for at least the past 6
weeks; pain provoked by at least 2 of the
following activities: prolonged sitting or
kneeling, squatting, running, hopping, or
stair walking and tenderness on palpation of
the patella.
2,220/2846
(77.3%)
Point prevalence 153/2,062 (7.4%).
Steinberg
(2012) [31]
1/3 Non-professional female dancers,
aged 8–20, Israel (mean age 13.7
years).
1,359 Pain reproduced during clinical
examination; knee swelling was evident, or a
positive grinding sign and/or a positive
Patellar Inhibition Test (PIT) was obtained
when the knee and especially the patella
were palpated, contracted and stretched.
1,359/1,359
(100%)
Point prevalence 321/1,359 (23.6%).
(Continued)
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 8 / 18
Discussion
Summary of main findings
The results of this systematic review confirm that PFP is a common pathology among adoles-
cents, the general population, and those with high levels of activity, such as elite athletes and
military populations. Point prevalence within military populations is reported as 13.5% [13];
female general populations 12% to 13% [5]; multi-day amateur cyclists 35% [24]; and female
elite sports 16.7% to 29.3% [11,85]. It was calculated through meta-analysis to be 7.2% in
mixed sex adolescents, and 22.7% in female amateur athletes. Annual prevalence in the general
population is reported as 22.7% [83]; in professional cyclists it is reported as 35.7% [13]; and in
general adolescent population it is reported as 28.9% [27]. No studies that were included
within our review reported life-time prevalence.
To our knowledge, this is the first review to systematically evaluate and synthesise incidence
and prevalence data for PFP. Comparison between studies was fulfilled in relation to age, sex,
and activity levels (general population, military and elite athletes).
Clinical implications
Patellofemoral pain is often cited as an overuse injury [86], with short periods of overuse or an
increase in physical activity thought be a particular risk factor [87]. Within the military popu-
lation there was low agreement on incidence rate, with predominantly male recruits reported
in five studies at 9.7–571.4 cases per 1,000 person-years [17,32,7981]. Of note is the study
with the highest reported incidence (571.4/1,000 person-years) originated from a country with
military conscription [17], and may have a population comprising of participants not accus-
tomed to intense periods of physical activity. Studies with lower reported incidences (9.7–
349.1/1,000 person-years) were from countries without conscription, where high levels of
physical fitness are a requirement of recruitment [13,32,7981], and so may contain partici-
pants more accustomed to intense periods of physical activity. Within the general population
the 10-week incidence for novice runners was comparable to the incidence in conscripted mil-
itary recruits, at 1080.5 cases per 1,000 person-years [82]. These data seem to be in agreement
with the model that attributes short periods of unaccustomed high levels of physical activity as
Table 3. (Continued)
Study Quality
score
Study population Sample
Size
Case definition Response
rate
Results
Elite
Athletes
Clarsen
(2010) [12]
2/3 Professional cycling; 7 training
camps (100% male; mean age 26)
109 Cyclist reported complaint of anterior knee
pain in the last 12 months, of any duration.
Cyclist reported complaint of anterior knee
pain in the last 12 months, >30 days
109/109
(100%)
Annual prevalence 39/109 (35.8%).
Annual prevalence 7/109 (6.4%).
Nejati
(2010) [11]
1/3 Female athletes participating in 3
rd
Iranian Sports Olympiad (mean
age 21.6, range 15–35).
418 Non traumatic anterior knee pain of at least
3 months duration that was felt retropatellar
or peripatellar and was aggravated by
descending or ascending stairs, squatting or
prolonged sitting.
418/
unknown
Point prevalence was 70/418 (16.7%).
Winslow
(1995) [85]
1/3 University female ballet dancers,
USA (mean age unknown)
41 Pain in front of or under the knee cap with 3
out of 5: associated with kneeling; squatting;
during stair climbing; sensations of
cracking/grinding or with incidents of joint
locking or "catching."
41/
unknown
Point prevalence was 12/41 (29.3%).
Information not within publication, authors contacted for clarification.
https://doi.org/10.1371/journal.pone.0190892.t003
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 9 / 18
a risk factor for development of PFP. Contemporary thinking in relation to training loads and
injury risk challenges the idea that PFP is simply an overuse injury, with evidence suggesting
that under-training may be a risk factor for an increase in injury risk in athletes [88]. Exposure
to appropriate training loads and periodisation, without ‘spikes’ in training, is thought to be
one method of risk management [88].
There was some consistency in the data relating to ratios of females to males, seemingly
confirming the commonly cited claim that females are twice as likely to develop PFP than
males [14]. One study demonstrated that females were approximately twice as likely to develop
PFP as males during military training, however the same study also demonstrated no statistical
difference in point prevalence between males (12.3%) and females (15.3%) (p= 0.09) prior to
the start of the training programme; suggesting that the transition to elite military fitness from
the general population is an important factor in PFP [13]. Another study reported point preva-
lence within the general population as 29.2% in females and 15.5% males [83]. Prevalence
comparison between sexes for adolescents also demonstrates this phenomenon, with one
Table 4. Quality appraisal.
The study sample represents the population of interest on key
characteristics
Was there an
adequate
response
rate?
Was the case definition specified and is it
reproducible?
Boling (2010) [13] ✓ ✓
Clarsen (2010) [12] ✓ ✓
Coppack (2011)
[79]
✓ ✓
Devan (2004) [26] X ✓ ✓
Dey (2016) [83] ✓ ✓
Fairbank (1984)
[27]
X X
Finnoff (2011) [28]X
Hall (2015) [29] X ✓ ✓
Herbst (2015) [30] X X
Kaufman (1999)
[80]
X✓ ✓
Milgrom (1991)
[17]
XX
Molgaard (2011) [9] ✓ ✓
Myer (2010) [16] X ✓ ✓
Nejati (2010) [11] X Unknown
Rathleff (2014) [84] ✓ ✓
Roush (2012) [5] ✓ ✓
Steinberg (2012)
[31]
XX
Thijs (2011) [82] X ✓ ✓
Thijs (2007) [32] ✓ ✓
Weiss (1985) [24] ✓ ✓
Wills (2004) [81] ✓ ✓
Winslow (1995)
[85]
X Unknown
Witvrouw (2000)
[18]
Unknown X
, yes; X, no
https://doi.org/10.1371/journal.pone.0190892.t004
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 10 / 18
study showing that females made up 69% of participants with PFP, compared with 31% in
males [9]. This is confirmed by our pooled estimates of point prevalence, with mixed sex being
calculated at 16.3% and female only at 22.7%.
These data may be used to identify possible populations who are at risk, which may help in
relation to clinical decision-making, and the allocation of healthcare and research funding,
such as adolescents and people attempting to increase physical activity levels. These popula-
tions may be at increased risk of developing of PFP, with subsequent development of pain and
physical disability, and possible withdrawal from physical activity. As a consequence having
reduced physical activity levels with loss of associated health benefits [8991].
Research implications
There appears to be a large discrepancy with research funding and priorities for PFP compared
with other knee conditions. For example, there have been over 14,000 papers indexed in MED-
LINE for knee osteoarthritis in the last 20 years, with only 1,500 papers indexed on PFP. Yet
despite these large differences, incidences rates for PFP far exceed those reported for knee oste-
oarthritis. This review found reported incidences rates across all populations of 9.7–1080.5
cases per 1,000 person-years; based on primary-care data in Spain the incidence rates for knee
osteoarthritis is reported as 8.3 cases per 1,000 person-years for females and 4.6 cases per 1,000
person-years for males, far lower than that of PFP [92]. Furthermore, disability, function and
pain scores are comparable; disability and function as measured with the Knee injury and
Osteoarthritis Outcome Scores (KOOS) [93], are similar with both conditions [84,94,95]; like-
wise pain on activity, as measured on a 100mm visual analogue scale, is equivalent [96,97].
Additionally, PFP often affects younger populations, with a significant degree of persistence,
potentially making it a much more significant problem, with work absenteeism, and long term
health implications through loss of physical activity [8991].
One of the barriers research and healthcare funding faces for PFP is that historically it has
been labelled a “benign, self-limiting condition” [98]. An influential 1985 cohort study by San-
dow and Goodfellow [98], that followed 54 adolescents for two to eight years with a new diag-
nosis of PFP, concluded that a policy of non-intervention was justified in the management of
this condition, and that the condition improved over time with few reporting disability. This
interpretation contrasts with the APA2011 cohort from Denmark [99]. They demonstrated
that at two year follow-up, adolescents with PFP are more likely to still be reporting pain than
people with other knee conditions [99]. Indeed, a recent re-analysis of Sandow and Goodfel-
low’s data does not seem to support their own conclusions, with Luhann et al. [100] highlight-
ing that of the original 54 adolescents, 94% still had pain at final follow-up, with 54% reporting
same or worse severity of symptoms. This pattern of poor long term prognosis continues in
the adult populations, with a large proportion (>50%) of people still reporting pain and dys-
function five to eight years after a six weeks evidenced based treatment programme [101]; yet
the impression that PFP is a benign and self-limiting condition, with non-intervention
advised, has continued to guide funders and stakeholders decision making for decades [102].
In the context of the high incidence and prevalence numbers, poor long term prognosis and
high disability levels, PFP should be an urgent research priority.
There is a pressing need for new studies into this condition. For example, advocates of qualita-
tive research methods suggest that qualitative inquiry can disclose the lived experience of people
with pain; and therefore be used to understand patient motivation, social engagement and provide
a wealth of information about the sociocultural context to pain [103,104]; to date no qualitative
body of work has been published on PFP. Qualitative inquiry can provide an insight that may lead
to development of ideas and hypothesis generation within the context of the contemporary
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 11 / 18
biopsychosocial model of pain. This could then be used to develop new conservative management
approaches that could then be tested with efficacy and effectiveness trials.
Strengths and limitations of included trials
A systematic and rigorous approach was taken to identify relevant studies, which included
electronic database searching, hand searching, citation searching; with endeavour to find un-
published studies.
The main sources of heterogeneity within the included studies were likely to be from differ-
ence in populations and ages. Other potential sources of heterogeneity are different study
design methodologies, for example the nature of measures such as point or period, and differ-
ences in case definitions. There was no consistency within the included studies on the case def-
inition used, with no two the same. Historically PFP was considered a separate pathology to
intra-articular pathologies such as: bursitis, plica syndromes and chondromalacia patellae
[105]; however several studies recently have demonstrated that structural abnormalities of the
patellofemoral joint on Magnetic Resonance Imaging (MRI) are not associated with PFP
[106,107], and a recent consensus statement from the 4th International Patellofemoral Pain
Research Retreat defined PFP subjectively only, with no essential objective findings [4]. How-
ever, only seven of the included 23 studies in this review had a contemporary case definition
that omitted objective findings [11,16,27,81,8385].
Limitations of this review
The study presented with two key limitations. For pragmatic reasons only one reviewer
screened titles and abstracts. An extensive literature search was carried out, with two reviewers
independently screening full-texts for inclusion, and two reviewers independently extracting
the data. An attempt was made to retrieve unpublished trials; however it may be that not all tri-
als were retrieved, particularly considering we did not search for papers published in languages
other than English. It is likely that the inclusion of such data could influence the estimates of
incidence and prevalence for PFP.
Conclusion
PFP is a common condition, with approximately one in 10 military recruits and one in 14 ado-
lescents suffering at any one time; and one in five of the general population experiencing pain
within the last year. Due to a paucity of evidence uncertainty remains with regards to these
estimates of incidence and prevalence, and further published or unpublished work is likely to
revise our estimates. There is some consistency with data showing females are twice as likely to
experience PFP as males. In the context of high incidence and prevalence numbers, poor long
term prognosis and high disability levels, PFP should be an urgent research priority. GPs need
to be aware of high risk groups, such as adolescents and adults increasing physical activity lev-
els, and the persistent nature of the problem, and ensure timely referrals to physiotherapy to
maintain physical activity levels.
Supporting information
S1 File. PRISMA checklist.
(DOCX)
S1 Fig. PRISMA flowchart.
(TIFF)
Incidence and prevalence of patellofemoral pain
PLOS ONE | https://doi.org/10.1371/journal.pone.0190892 January 11, 2018 12 / 18
Author Contributions
Conceptualization: Benjamin E. Smith.
Formal analysis: Benjamin E. Smith.
Funding acquisition: Benjamin E. Smith.
Investigation: Benjamin E. Smith, James Selfe, Damian Thacker.
Methodology: Benjamin E. Smith, James Selfe, Damian Thacker, Paul Hendrick, Marcus Bate-
man, Fiona Moffatt, Michael Skovdal Rathleff, Toby O. Smith, Pip Logan.
Project administration: Benjamin E. Smith.
Validation: Damian Thacker.
Writing – original draft: Benjamin E. Smith.
Writing – review & editing: Benjamin E. Smith, James Selfe, Damian Thacker, Paul Hendrick,
Marcus Bateman, Fiona Moffatt, Michael Skovdal Rathleff, Toby O. Smith, Pip Logan.
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Supplementary resources (2)

... Finally, it can lead to local muscle atrophy due to the destruction of nerve tissues, generating a loss of function and inability to perform movements without pain [3][4][5][6]. According to Smith (2018), the prevalence of PFPS in the general population is 22.7% and can be classified as Musculoskeletal Disorder (MSD) class two or three (MSD-2 or MSD-3) when in an occupational context [7]. In the European Working Conditions Survey's report (EWCS 2015), it is observed that the frequency of Work-Related MSD (WRMSD) on lower limbs is higher, 29% in men and 30% in women [8]. ...
... A Syndrome such as PFPS is characterized by a set of diseases with similar symptoms that significantly impact the person's life [10,11]. When analysing it, it is observed that there is very little information in the literature and even less when looking for specific information on worker populations [12]. To clarify the present knowledge about this problem, the objective of this study is to evidence the prevalence of PFPS in different occupational realities in non-athlete workers. ...
Conference Paper
Full-text available
The Patellofemoral Pain Syndrome in an occupational context is an important topic to be discussed. There is a lack of information in the scientific literature, especially when dealing with populations of non-athlete workers. Its main objective is to find evidence in the literature of the prevalence of Patellofemoral Pain Syndrome in non-athlete workers from different economic sectors. This systematic review only uses studies that showed the prevalence of Patellofemoral Pain Syndrome in non-athlete workers as inclusion criteria. It is considered the population over 18 years old, without gender restriction, healthy or not, diagnosed by physicians based on clinical and/or radiological criteria. Searches were carried out in Scopus, Academic Search Complete, Science Direct, Web of Science, PMC, PubMed, Informaworld and Medline. The last search was in January 2022. The risk of bias in the selected articles was analyzed using the RoB 2.0 tool (Revised Cochrane risk-of-bias tool for randomized trials. It was verified the existence of a variation in prevalence from 1.08% to 34.9% between data collected in different studies. The main limitation of the research was the number of detected studies, only 7. However, this same fact made it possible to highlight the need for more research on populations of workers and demonstrate the general need for more studies in the area. The research is registered in PROSPERO under the number CRD42021276885.
... Patellofemoral pain syndrome (PFPS) is a non-traumatic musculoskeletal condition found in diverse populations, particularly among women. 1,2 The high incidence rate of PFPS in clinical settings has been extensively described. A high estimate of 22.7% in the general population and 28.9% in adolescents was reported in 2018. 1 Strong evidence indicates that the hip muscles play a crucial role in controlling and managing femoral excursions in both the frontal and transverse planes. ...
... A high estimate of 22.7% in the general population and 28.9% in adolescents was reported in 2018. 1 Strong evidence indicates that the hip muscles play a crucial role in controlling and managing femoral excursions in both the frontal and transverse planes. 3,4 Additionally, individuals with PFPS have poor isometric and dynamic hip abductor and extensor strength. ...
... PFPS prevalence in the general population is about 22.7% (Smith et al. 2018). However, it may be higher in specific populations, e.g. ...
Chapter
Patellofemoral pain syndrome (PFPS) is a musculoskeletal disorder in the anterior region of the knee, affecting people of different ages. When it is necessary to go up and down many stairs in a work context, there is a risk of increased wear on the knee joint and, consequently, PFPS. The main objective of this work was to identify the risk of contracting PFPS associated with the action of going up and down stairs in the workplace. An analysis of workers’ movement on an oil platform without lifts was carried out in the circulation by stairs between the different floors. It has been found that leg movements made when going up and down stairs can be harmful to the knee joints. A recommendation was made to change the way workers go up and down stairs to reduce the overload on the joint knee and the risk of contracting or worsening PFPS.
... About 29% of adolescents have knee pain [1]. One of the underlying causes of this pain is a combination of femoral and tibial torsion, which is often leading to functional limitations and to the cessation of sports activities [2]. ...
... Patellofemoral Pain (PFP) is a multifactorial condition and the most common diagnosis in physically active populations (Baquie & Brukner, 1997;Taunton et al., 2002). PFP's annual prevalence in the general population and specifically in females was reported as 22% and 29%, respectively (Smith et al., 2018). In addition, women were two times more likely to develop PFP compared with men (Boling et al., 2010). ...
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.
Article
Full-text available
Background: Patellofemoral pain syndrome (PFPS) is the anterior or retro patellar pain that can be precipitated by some daily activities such as ascending and descending stairs, kneeling, squatting or performing everyday tasks and is a multifactorial condition. Objective to investigate the relationship between nerve conduction velocity of femoral nerve and its mechanosensitivity changes such as (limited hip extension range of motion (ROM) & pain) in patients with PFPS Methods: Thirty symptomatic individuals with PFPS and 30 healthy individuals as a control group were assessed through sensory surface nerve conduction velocity of femoral nerve and measuring the hip extension (ROM) with the level of pain on Numeric rating scale (NRS) during femoral slump test. Main Outcome measures: All of the participants in both groups were underwent the sensory conduction test (Peak Latency and conduction velocity) and the femoral slump test (Hip extension ROM & pain level on NRS). Results: There were no significant difference between groups regarding hip extension ROM during femoral nerve slump test (p =0.57), while the pain associated with femoral nerve was higher in PFPS group than control group (p =0.000), also, femoral nerve velocity measured using EMG was lowered in PFPS group in comparison with healthy individuals while the initial latency was delayed and prolonged in PFPS than their control counter partners , (p =0.000), (p =0.000) There was a significant moderate negative correlation between NRS during femoral nerve slump test and hip ROM (p=0.007, r =-0.48), and femoral nerve velocity using EMG study (p=0.005, r =-0.502). There was a significant moderate positive correlation between NRS during femoral nerve slump test and femoral nerve latency using EMG study (p=0.003, r = 0.523) Conclusion: There is a significant difference in femoral nerve mechanosensitivity among individuals with PFPS. Also there was a significant difference in conduction velocity of the femoral neve among individuals with PFPS compared to control group and There was a significant moderate negative correlation between NRS during femoral nerve slump test and hip ROM, and femoral nerve velocity using EMG study. As well rehabilitation programs for those with PFPS should include neurodynamic techniques for femoral nerve or (femoral nerve gliding). Finally femoral NCV may be used as a gold standard method for assessing femoral nerve mechano-sensitivity changes in those with resistant PFPS .
Article
Objective: To determine the effects of non-surgical treatments on pain and function in people with patellofemoral pain (PFP). Design: Systematic review with meta-analysis. Literature search: We searched Medline, Web of Science, and Scopus to May 2022 for interventional randomised controlled trials (RCTs) in people with PFP. Study selection criteria: We included RCTs that were scored >7 on the PEDro scale. Data synthesis: We extracted homogenous pain and function data at short- (<3 months), medium- (>3 to <12 months) and long-term (>12 months) follow up. Interventions demonstrated primary efficacy if outcomes were superior to sham, placebo, or wait-and-see control. Interventions demonstrated secondary efficacy if outcomes were superior to an intervention with primary efficacy. Results: We included 65 RCTs. Four interventions demonstrated short-term primary efficacy: knee-targeted exercise therapy for pain (SMD 1.16, 95% CI 0.66, 1.66) and function (SMD 1.19, 95% CI 0.51, 1.88), combined interventions for pain (SMD 0.79, 95% CI 0.26, 1.29) and function (SMD 0.98, 95% CI 0.47, 1.49), foot orthoses for global rating of change (OR 4.31, 95% CI 1.48, 12.56), and lower-quadrant manual therapy for pain (SMD 2.30, 95% CI 1.60, 3.00). Two interventions demonstrated short-term secondary efficacy compared to knee-targeted exercise therapy: hip-and-knee-targeted exercise therapy for pain (SMD 1.02, 95% CI 0.58,1.46) and function (SMD 1.03, 95% CI 0.61, 1.45), and knee-targeted exercise therapy and perineural dextrose injection for pain (SMD 1.34, 95% CI 0.72, 1.95) and function (SMD 1.21, 95% CI 0.60, 1.82). Conclusion: Six interventions had positive effects at three-months for people with PFP, with no intervention adequately tested beyond this timepoint.
Article
Background Anterior knee pain following total knee arthroplasty (TKA) is associated with patient dissatisfaction. Factors related to post-operative anterior knee pain and its impact on patient outcomes are poorly understood. We aimed to: (i) report the prevalence of anterior knee pain before and after TKA using a posterior-stabilized prosthesis with routine patellar resurfacing; (ii) investigate the association of pre-operative clinical factors with the presence of anterior knee pain after TKA; (iii) explore the association of post-operative anterior knee pain with post-operative self-reported function and quality of life. Methods This retrospective study included 506 patients who had undergone elective primary unilateral TKA with a posterior stabilized prosthesis and patellar resurfacing. Outcome measures prior to and 12 months after TKA included self-reported anterior knee pain, knee function and quality of life. Results Prevalence of anterior knee pain was 72% prior to and 15% following TKA. Patients who had pre-operative anterior knee pain had twice the risk of experiencing anterior knee pain after TKA than patients who did not have pre-operative anterior knee pain (risk ratio: 2.37; 95% Confidence Interval = 1.73 to 2.96). Greater severity of pre-operative anterior knee pain and worse self-reported function were associated with the presence of post-operative anterior knee pain (rho = 0.15, p<0.01; rho = 0.13, p<0.01, respectively). Pre-operative age, sex, and quality of life were not associated with post-operative anterior knee pain. Greater severity of post-operative anterior knee pain was associated with worse knee function at 12 months post-operative (rho = 0.49, p<0.01). Conclusion One in seven patients reported anterior knee pain 12-months following posterior stabilized and patella-resurfaced TKA. The presence of pre-operative anterior knee pain and worse self-reported function are associated with post-operative anterior knee pain.
Article
Full-text available
Objective: To determine the effects of McConnell taping combined with strengthening exercises on Q angle and intensity of pain in females with patellofemoral Pain Syndrome. Study Design: Randomized control trial Place and Duration of Study: Physical Medicine & Rehabilitation department of Fauji Foundation Hospital st st Rawalpindi from 1 Jan to 31 June 2018. Materials and Methods: Females with patellofemoral pain syndrome with age 25-45 years, having anterior knee pain, limited/painful knee Range of motion and increased Q angle>18 were included in the study through non-probability convenience sampling technique .Numeric Pain Rating Scale(NPRS)and Goniometry tools were used to measure the outcomes. A total of 70 approached cases only 48 met the inclusion criteria, out of which 40 subjects completed the treatment protocol. Subjects were divided randomly in to experimental and control groups. Both groups received standard treatment protocol including Trans Cutaneous Electrical Nerve (TENS) and Heating Pad for 15 minutes while Experimental group received McConnell taping in addition. Data was analyzed by using SPSS Version 21. Results: There was significant improvement in pain intensity and Q angle in experimental group after McConnell taping p value was <0.05 for pain. Flexion ROM was significantly improved in both groups p<0.05.while extension ROM was in normal Range pre and post treatment p<0.05. Conclusion: Results of this study shows that McConnell taping reduces pain intensity and Quadriceps Angle in patients with patellofemoral pain syndrome.
Article
Objectives To systematically evaluate the literature and estimate the prevalence, incidence, and burden of gradual-onset knee injuries in team ball-sports. Design Systematic review with meta-analysis. Method Six databases (MEDLINE, EMBASE, Web of Science, CINAHL, SPORTDiscus, SCOPUS) were searched from inception to June 2021. Cohort studies of team ball-sports reporting the number of gradual-onset knee injuries were included. Study quality was assessed using a modified Newcastle-Ottawa scale. Studies were pooled using a Freeman-Tukey Double arcsine transformation (prevalence) and a Poisson random effects regression model (incidence, burden). Results Forty-nine studies that captured gradual-onset knee injuries (unclassified, patellofemoral pain, tendinopathies, and iliotibial band friction syndrome) across 15 team ball-sports were included. For unclassified gradual-onset knee injuries, prevalence was 4 % (95 % Confidence Interval (CI) 2 % to 7 %, I² = 96 %), incidence was 0.32 per 1000 player-hours (95 % CI 0.25 to 0.43, I² = 88 %), and burden was 3.24 days lost per 1000 player-hours (95 % CI 1.95 to 5.37, I² = 99 %). For patellofemoral pain, prevalence was 6 % (95 % CI 1 % to 13 %, I² = 93 %), and incidence was 0.07 per 1000 player-hours (95 % CI 0.04 to 0.12, I² = 67 %). For tendinopathies, prevalence was 1 % (95 % CI 0 % to 2 %, I² = 68 %), incidence was 0.07 per 1000 player-hours (95 % CI 0.04 to 0.11, I² = 76 %), and burden was 2.14 days lost per 1000 player-hours (95 % CI 1.23 to 3.71, I² = 92 %). Conclusion Estimates of prevalence, incidence and burden generated from this systematic review quantify the extent of gradual-onset knee injuries in team ball-sports. Further research is required to assess whether age, sport, and participation level are predictors of gradual-onset knee injuries.
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Background In spite of the high rate of overuse injuries in ballet dancers, no studies have investigated the prevalence of overuse injuries in professional dancers by providing specific diagnoses and details on the differences in the injuries sustained as a function of age and/or years of professional practice. Hypothesis Overuse injuries are the most prevalent injuries in ballet dancers. Professional ballet dancers suffer different types of injuries depending on their age and years of professional practice. Study Design Descriptive epidemiology study. Methods This descriptive epidemiological study was carried out between January 1, 2005, and October 10, 2010, regarding injuries sustained by professional dancers belonging to the major Spanish ballet companies practicing classical, neoclassical, contemporary, and Spanish dance. The sample was distributed into 3 different groups according to age and years of professional practice. Data were obtained from the specialized medical care the dancers received from the Trauma and Orthopaedic Surgery Service at Fremap in Madrid. The dependent variable was the study of the injury. Results A total of 486 injuries were identified over the study period, with overuse injuries being the most common etiology (P < .0001); these injuries were especially prevalent in junior professional dancers practicing classical ballet and veteran dancers practicing contemporary ballet (P = .01). Specifically, among other findings, stress fractures of the base of the second metatarsal (P = .03), patellofemoral syndrome, and os trigonum syndrome were more prevalent among junior professionals (P = .04); chondral injury of the knee in senior professionals (P = .04); and cervical disc disease in dancers of intermediate age and level of experience. Conclusion Overall, overuse injuries were more prevalent in younger professionals, especially in women. This finding was especially true for the more technical ballet disciplines. On the other hand, in the athletic ballet disciplines, overuse lesions occurred mainly in the more senior professionals. Clinical Relevance This study provides specific clinical diagnoses obtained through physical examination as well as details on the different injury types sustained as a function of age and/or years of professional practice, an important aspect for ballet and sports practice in general.
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Background Patellofemoral pain is one of the most common conditions seen in sports medicine practices, particularly among adolescent females. However, the natural history of the underlying pathology in patellofemoral pain during puberty remains poorly understood. Purpose The purpose of this longitudinal study is to assess changes in patellar maltracking patterns in subjects with patellofemoral pain as they mature from mid- to late adolescence. Study Design Cohort study; Level of evidence, 3. Methods Three-dimensional patellofemoral kinematic data were acquired during active knee extension-flexion using dynamic magnetic resonance imaging in 6 girls (10 knees; mean age, 14.0 years) with clinically diagnosed patellofemoral pain. The subjects then returned as late adolescents (mean age, 18.5 years) for follow-up scanning. Three-dimensional patellofemoral kinematic parameters were evaluated across the range of motion, but comparison between time points was restricted to 10° of flexion. Participation in impact and nonimpact physical activities, pain score based on the visual analog scale, and the anterior knee pain score were also compared across initial and follow-up visits. Results All subjects reported improved patellofemoral pain symptoms at follow-up, and one subject reported complete resolution. However, relative to the initial visit, no differences were found in patellar maltracking. There was a decrease in hours engaged in impact physical activities for all subjects at follow-up. Conclusion This study provides insight into the natural history of patellofemoral pain in adolescent females. The relatively unchanged patellofemoral maltracking across subjects suggests that potential anatomic and kinematic abnormalities contributing to patellofemoral pain during mid-adolescence persist during skeletal maturation. Symptom improvement for these subjects did not result from a change in patellofemoral tracking, but rather from other causes.
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Introduction: Bicycling is one of the most enjoyable aerobic exercises recommended for the promotion of an individual′s health. The Eastern Province of Saudi Arabia has seen a huge increase in the number of people who cycle. People have different goals for bicycling, but the injuries they sustain are common. Most of them relate to overuse, particularly of lower body joints. This study was conducted to determine the prevalence of knee problems and factors associated with knee pain in cyclists. Materials And Methods: A cross-sectional study was conducted in October 2015, using an online self-administered questionnaire. The questionnaire was based on pertinent literature, was piloted, and validated. A web link was sent to 513 cyclists (professional and amateur) using E-mail, WhatsApp application, or SMS. Three hundred and eleven responses were received, 283 of which were included in the analysis. Results: The overall prevalence of knee pain was 25.8%; 27.6% for amateur cyclists and 15.9% for professional cyclists. Only 17.2% knee pain was attributed to cycling, whereas in 32.8% it happened spontaneously and in 25% of cases it occurred while running. Majority of the cyclists reported pain as mild (61.6%) or moderate (28.7%); anterior knee pain accounted for 58.1% knee pain. Different goals of cycling and different bicycle types had statistically significant difference on the rate of knee pain. Of underweight cyclists, 62.2% reported knee pain. Cyclists who run more or participated in football had a higher rate of pain. Conclusion: Knee injuries are common with cyclists. Factors such as the type of the bicycle, the goal of bicycling, club type, body mass index, and participation in other sports play a significant role in the rate of knee pain.
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Background Community-based studies of patellofemoral pain (PFP) need a questionnaire tool that discriminates between those with and those without the condition. To overcome these issues, we have designed a self-report questionnaire which aims to identify people with PFP in the community. Methods Study designs: comparative study and cross-sectional study.Study population: comparative study: PFP patients, soft-tissue injury patients and adults without knee problems. Cross-sectional study: adults attending a science festival.Intervention: comparative study participants completed the questionnaire at baseline and two weeks later. Cross-sectional study participants completed the questionnaire once.The optimal scoring system and threshold was explored using receiver operating characteristic curves, test-retest reliability using Cohen’s kappa and measurement error using Bland-Altman plots and standard error of measurement. Known-group validity was explored by comparing PFP prevalence between genders and age groups. ResultsEighty-four participants were recruited to the comparative study. The receiver operating characteristic curves suggested limiting the questionnaire to the clinical features and knee pain map sections (AUC 0.97 95 % CI 0.94 to 1.00). This combination had high sensitivity and specificity (over 90 %). Measurement error was less than the mean difference between the groups. Test–retest reliability estimates suggest good agreement (N = 51, k = 0.74, 95 % CI 0.52–0.91). The cross-sectional study (N = 110) showed expected differences between genders and age groups but these were not statistically significant. ConclusionA shortened version of the questionnaire, based on clinical features and a knee pain map, has good measurement properties. Further work is needed to validate the questionnaire in community samples.
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A study was undertaken to document the incidence of overuse injuries sustained during basic military training. The injuries in military recruits (N = 1,261) undergoing basic training were documented prospectively over a 9-week period. Injury incidence was expressed as percentage of all recruits injured, weekly incidence (injuries/1,000 recruits/week), and injuries/ 1,000 training hours. The incidence of six common specific overuse injuries was also recorded. The overall incidence of injuries over the 9-week period was 31.9% (acute, 13.6%; overuse, 86.4%), or 1.8/1,000 training hours. The highest incidence of injuries was recorded in weeks 1 to 3 and week 9 of training, which were weeks characterized by marching (>77% of the training time). The highest incidence (injuries/1,000 training hours) of specific overuse injuries were tibial bone stress reaction (0.33), patellofemoral pain (0.22), and the iliotibial band friction syndrome (0.08). The incidence of stress fractures over the 9-week period was 1.2% (0.07/1,000 training hours). Injuries to the knee, lower leg, and ankle accounted for more than 80% of all injuries. A total of 3.6% of training days were lost during this period, mainly due to bone stress injuries. In order to reduce injuries during basic military training, attention must be directed towards (1) modifying the type of training and (2) prevention of bone stress injuries.
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The aim of the article is to provide an indication of anterior knee pain prevalence among young South African basketball players. A retrospective questionnaire survey was conducted to capture information on injuries sustained over one season. The sample comprised 458 young basketball players in Cape Town and comprised 122 club players and 337 school basketball players. A total of 180 knee injuries were reported indicating a rate of 1 knee injury in 2.5 players. Anterior knee pain was the most commonly reported area ofpain by the 458 basketball players (49.1%, n=141). The most common combination of pain area was anteromedially (18.2%, n=141). The results of our survey are in agreement with other studies indicating that patellofemoral pain is probably the most common knee presentation among young active individuals and arguably the most common condition seen at sports injury clinics.
Article
Background: Structural abnormalities of the patellofemoral joint might play a role in the pathogenesis of patellofemoral pain (PFP), a common knee problem among young and physically active individuals. No previous study has investigated if PFP is associated with structural abnormalities of the patellofemoral joint using high-resolution magnetic resonance imaging (MRI). Purpose: To investigate the presence of structural abnormalities of the patellofemoral joint on high-resolution MRI in patients with PFP compared with healthy control subjects. Study design: Cross-sectional study; Level of evidence, 3. Methods: Patients with PFP and healthy control subjects between 14 and 40 years of age underwent high-resolution 3-T MRI. All images were scored using the Magnetic Resonance Imaging Osteoarthritis Knee Score with the addition of specific patellofemoral features. Associations between PFP and the presence of structural abnormalities were analyzed using logistic regression analyses adjusted for age, body mass index (BMI), sex, and sports participation. Results: A total of 64 patients and 70 control subjects were included in the study. Mean ± SD age was 23.2 ± 6.4 years, mean BMI ± SD was 22.9 ± 3.4 kg/m(2), and 56.7% were female. Full-thickness cartilage loss was not present. Minor patellar cartilage defects, patellar bone marrow lesions, and high signal intensity of the Hoffa fat pad were frequently seen in both patients (23%, 53%, and 58%, respectively) and control subjects (21%, 51%, and 51%, respectively). After adjustment for age, BMI, sex, and sports participation, none of the structural abnormalities were statistically significantly associated with PFP. Conclusion: Structural abnormalities of the patellofemoral joint have been hypothesized as a factor in the pathogenesis of PFP, but the study findings suggest that structural abnormalities of the patellofemoral joint on MRI are not associated with PFP.