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Which factors differentiate athletes with hip/groin
pain from those without? A systematic review with
meta-analysis
Andrea B Mosler,
1,2
Rintje Agricola,
3
Adam Weir,
4
Per Hölmich,
4,5
Kay M Crossley
2,6
▸Additional material is
published online only. To view
please visit the journal online
(http://dx.doi.org/10.1136/
bjsports-2015-094602).
1
Rehabilitation Department,
Aspetar Orthopaedic and
Sports Medicine Hospital,
Doha, Qatar
2
School of Health and
Rehabilitation Sciences,
University of Queensland,
Brisbane, Australia
3
Department of Orthopaedics,
Erasmus University Medical
Centre, Rotterdam,
the Netherlands
4
Sports Groin Pain Centre,
Aspetar Orthopaedic and
Sports Medicine Hospital,
Doha, Qatar
5
Arthroscopic Center Amager,
SORC-C, Copenhagen
University Hospital,
Amager-Hvidovre, Denmark
6
School of Allied Health,
La Trobe University, Victoria,
Australia
Correspondence to
Professor Kay M Crossley,
School of Allied Health,
College of Science, Health and
Engineering, La Trobe
University, Bundoora, Victoria
3068, Australia;
k.crossley@latrobe.edu.au
Accepted 4 April 2015
To cite: Mosler AB,
Agricola R, Weir A, et al.Br
J Sports Med 2015;49:810.
ABSTRACT
Background Hip and groin injuries are common in
many sports. Understanding the factors differentiating
athletes with hip/groin pain from those without these
injuries could facilitate management and prevention.
Objective Conduct a systematic review and meta-
analysis of the literature on factors differentiating
athletes with and without hip/groin pain.
Methods The review was registered as PROSPERO
CRD42014007416 and a comprehensive, systematic
search was conducted in June 2014. Inclusion criteria
were: cross-sectional, cohort or case–control study
designs of n>10 that examined outcome measures
differentiating athletes with and without hip/groin pain.
Two authors independently screened search results,
assessed study quality, and performed data extraction.
Methodological heterogeneity was determined and data
pooled for meta-analysis when appropriate. A best
evidence synthesis was performed on the remaining
outcome measures.
Results Of 2251 titles identified, 17 articles were
included of which 10 were high quality. Sixty two
different outcome measures were examined, 8
underwent meta-analysis. Pooled data showed strong
evidence that athletes with hip/groin pain demonstrated:
pain and lower strength on the adductor squeeze test,
reduced range of motion in hip internal rotation and
bent knee fall out; however, hip external rotation range
was equivalent to controls. Strong evidence was found
that lower patient-reported outcome (PRO) scores,
altered trunk muscle function, and moderate evidence of
bone oedema and secondary cleft sign were associated
with hip/groin pain.
Conclusions PROs, pain and reduced strength on the
adductor squeeze test, reduced range of motion in
internal rotation and bent knee fall out are the outcome
measures that best differentiate athletes with hip/groin
pain from those without this pain.
INTRODUCTION
Hip and groin pain is problematic for athletes, par-
ticularly in sports involving high loads of running,
change of direction and kicking. Groin pain is the
third most common injury in both soccer and
Australian Rules football, accounting for 4–16% of
all injuries sustained per season.
12
It is also fre-
quent in other football codes, such as Rugby
League,
3
Gaelic Football
45
and American
Football,
6
as well as ice hockey.
7
The aetiology is
multifactorial, with coexisting pathological pro-
cesses occurring in different tissues.
8–11
Varying
approaches have been recommended to systematic-
ally examine and diagnose groin pain in an
athlete.
11–13
While the reliability of the tests used
in these approaches has been examined,
14–16
there
remains a lack of consensus on the terminology and
diagnostic categories used.
Intrinsic risk factors for hip/groin pain in athletes
have been prospectively studied.
317–23
Two system-
atic reviews identified only past history of injury
and lower adductor strength as risk factors, while
there is conflicting evidence for reduced hip range
of motion.
424
Injury prevention programmes
aimed at reducing the incidence of groin pain by
addressing these potentially modifiable risk factors
have had limited efficacy.
25–28
Hip and groin pain
still has a high incidence and recurrence rate.
17 23
Therefore, it seems that we do not yet fully under-
stand these injuries and further research is required
to assist in the understanding of injury mechanisms,
and factors contributing to the development of hip/
groin pain.
Injury prevention and management programmes
may be enhanced by knowledge of the factors dif-
ferentiating athletes with and without hip/groin
pain. Previous case–control and cohort studies
have examined the relationship between hip/
groin pain, and various clinical and radiological
features.
515–17 22 29–42
A systematic evaluation of
this literature may assist in the management and
prevention of this common athletic injury.
This study aimed to systematically review the lit-
erature examining the factors differentiating ath-
letes with and without hip/groin pain.
METHODS
This review followed the PRISMA guidelines and
the protocol was registered on the PROSPERO
International prospective register for systematic reviews
website (http://www.crd.york.ac.uk/PROSPERO) on 9
April 2014, with the following registration
number: CRD42014007416.
Eligibility criteria
Inclusion criteria were (1) case–control, cohort and
cross-sectional study designs, and (2) study of at
least one factor differentiating between athletic sub-
jects with hip/groin pain and those without. Hip/
groin pain participants were defined as those identi-
fied with having pain in the hip and groin region,
and encompassed the many different terminologies
used to describe athletic groin pain such as osteitis
pubis, long-standing groin pain, pubalgia, adductor-
related groin pain, and hip joint pain. Athletic
populations included people who participated in
any of the sports included under the MESH term
‘sports’plus marathon running. No restrictions
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Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602 1of12
Review
were placed on the duration of participant symptoms. In order
to reduce the potential risk of bias, a minimum number of 10
cases of hip/groin pain and control subjects were required.
Studies written in English, Dutch, German, Italian, French or
Spanish were included. Studies without a control group were
excluded from the review.
Search strategy
A comprehensive, systematic literature search was conducted on
20 June 2014, using the following electronic databases with no
date restrictions (1) EMBASE.com (2) MEDLINE (OvidSP) (3)
Cochrane (4) Web-of-science (5) Scopus (6) Cinahl (7) PubMed
publisher (8) Google Scholar and (9) Sport Discus. The com-
plete electronic search strategy is available in online supplemen-
tary material A. The literature search was assisted by a
biomedical information specialist (W.M. Bramer, Erasmus
University). The following key words were used for the search
with differing combinations: ‘hip’,‘inguinal’,‘groin’,‘pubalgia’,
‘pain’,‘sport’,‘team sport’,‘sport injury’,‘sports medicine’,
‘athlete’,‘athletic performance’plus the MESH term ‘sports’
plus marathon running. Search strategies were adapted as
required for each specific database
All potential references were imported into Endnote X4
(Thomson Reuters, Carlsbad, California, USA) and duplicates
removed. Title and abstracts were independently screened for
eligibility by two authors (ABM and RA). The full text of each
eligible published study was then independently examined given
the inclusion criteria and reference lists manually searched to
identify further relevant articles.
Quality appraisal
Two reviewers (ABM and RA) independently conducted meth-
odological quality assessment on each included article using the
modified Downs and Black scale (see online supplementary B),
which is appropriate for cohort and case–control study designs.
The Downs and Black scale is reliable
43
and the modified
version used in this study had a maximum score of 16.
44 45
The
methodological quality of each article was stratified, as in previ-
ous reviews,
45
with a total score ≥12 deemed to be high quality,
10 or 11 to be moderate quality, and low quality if the score
was ≤9. Disagreements in initial ratings of methodological
quality assessment were discussed between the two reviewers
(ABM, RA) and if required, a third reviewer (KMC) was con-
sulted to reach consensus.
Data extraction
All data from the included studies were independently extracted,
collated by consensus agreement, and entered into a predefined
Excel spread sheet by two reviewers (ABM, RA). If sufficient
data were not reported in the published article or online
supplementary material provided, the corresponding author was
contacted to request further data.
Study data were subdivided into the following categories:
patient reported outcome (PRO) measures, pain provocation
tests, range of motion, strength, trunk muscle function, radio-
logical measures, and other outcome measures.
Data synthesis and analysis
Data extraction of the included studies was conducted with
means and SDs calculated for continuous data for the hip/groin
and control participants separately. If data were not presented in
a manner enabling extraction, the corresponding author was
contacted to obtain the raw data. Where separate data were pre-
sented for both legs of control subjects; an average mean and
SD was calculated. For the case groups, data from the symptom-
atic leg were used if available or a mean (SD) of data from both
legs calculated if participants had bilateral symptoms or if the
symptomatic leg could not be determined. If more than one
method of measurement was used for a single outcome
measure, the data were extracted from the method used most
consistently between studies and/or determined to be most
reliable.
Methodological and clinical heterogeneity was evaluated for
all outcome measures and data pooled for meta-analysis as
appropriate. The software package from Review Manager
(RevMan) Version 5.3, Copenhagen: The Nordic Cochrane
Centre, The Cochrane Collaboration, 2014, was used to
conduct the meta-analysis. Standardised mean differences
(SMD) with 95% CIs were calculated for outcome measures of
continuous data and random effects models were used for each
meta-analysis. The magnitude of the effect size of the pooled
SMD was interpreted as large if SMD ≥0.8; moderate if 0.5–
0.8; weak if 0.2–0.5, and no effect determined if SMD≤0.2.
46
Statistical heterogeneity of the pooled data was examined
using the I
2
statistic. Sensitivity analysis was conducted by exam-
ining the forest plots of the pooled data following omission of
the data from each study, one by one.
For dichotomous data, an OR was calculated for the associ-
ation between a positive test and the presence of hip and groin
pain, and data pooled if methodological homogeneity was deter-
mined. Effect sizes for the OR were defined as follows: small
effect OR=1–1.25, medium effect OR=1.25–2 and large effect
OR≥2.
47
For outcome measures with methodological or clinical hetero-
geneity, qualitative data synthesis and analysis was performed.
For both quantitative and qualitative data synthesis, a level of
evidence was assigned to each outcome according to the recom-
mendations proposed by van Tulder et al.
48
RESULTS
Literature search
The electronic search identified 5269 records and following
removal of duplicates, the titles and abstracts of 2251 articles
were screened. The full text of 41 articles were retrieved and
assessed for eligibility against the inclusion criteria. Two articles
were added following citation checking.
36 37
After reviewing the
full text of 43 articles, 26 articles were excluded and the
remaining 17 articles
5151630–33 35–40 50–53
were included for
full review and data synthesis (figure 1).
Methodological quality
Two reviewers (ABM and RA) initially disagreed upon 21% of
the items of the 17 included studies (54 of 255 items).
However, all initial disagreements were discussed and consensus
reached on a final score for each paper, using the assistance of a
third reviewer (KMC) where required. The methodological
quality scores ranged from 8 to 15 out of maximum possible
score of 16, with the average score being 12 (see online supple-
mentary table S1). Ten of the included studies were of high
quality, 6 were of moderate quality and only 1 low quality study
was included for final data synthesis. Three studies scored posi-
tively on item 14 (sample size calculation) while 7 studies
reported blinding of assessors with respect to the presence of
hip/groin pain of the subjects (item 8).
2 of 12 Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602
Review
Characteristics of included studies
Table 1 presents the full characteristics of the included studies.
Data extraction was performed on all 17 of the included studies
and a detailed description of the studies is presented regarding
authors, year of publication, study design, participants (case and
control), diagnosis, symptom duration, outcome measure(s)
examined, method of measurement, differences between case
and control.
Factors differentiating athletes with and without hip/groin pain
Patient reported outcome measures
Several studies presented data from PROs, completed by both
control and hip/groin pain athletes.
530313652
None used iden-
tical PROs, but three high-quality studies assessed aspects of
pain using a Likert scale.
30 31 36
The Copenhagen hip and groin
outcome score (HAGOS) was used in one high-quality study,
5
while another high–quality study
52
used both the short form
(SF)-12, and the Hip Disability and Osteoarthritis Outcome
Score (HOOS). The results of the PROs are summarised in table 2.
All PROs were able to differentiate between athletes with and
without hip/groin pain, apart from the mental component
summary (MCS) of the SF-12. Synthesising these findings, there
is strong evidence that PROs can be used to differentiate athletes
with and without hip/groin pain.
Pain provocation tests
Five studies examined the difference between athletes with and
without hip/groin pain in response to various pain provocation
tests.
16 30 35 36 53
The pain on adductor squeeze testing was
recorded by 3 high-quality studies using the same methodology
(supine, resisted adduction at the medial knee with hips at 45°
flexion, and knees flexed 90°).
16 30 53
One of these studies
30
reported significantly greater pain experienced during the
squeeze test in the hip/groin pain group (p<0.001). However,
information on the number of groin pain athletes who experi-
enced pain with the squeeze test was not presented; therefore,
the data from this study could not be pooled. Data pooling
from the other 2 studies revealed a greater chance of being in
the hip/groin pain group if participants experienced pain during
the squeeze test with a large effect size; OR=4.31 (95% CI
1.86 to 10) figure 2. There is, therefore, strong evidence that
pain on the adductor squeeze test differentiates athletes with
hip/groin pain from those without pain.
The ORs for the other pain provocation tests examined in
single studies are: single adductor test (supine, leg straight and
resisted adduction at the ankle):
16
OR=4.03 (1.21–13.45), bilat-
eral adductor test (resisted bilateral adduction while athlete holds
both legs off the bed in 30° hip flexion):
16
OR=24.76 (5.35–
114.6), active straight leg raise test:
36
OR=56.64 (3.27–980.14),
Figure 1 Flow diagram for search
results and study selection.
Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602 3 of 12
Review
Table 1 Characteristics of included Studies (figures displayed as mean±SD unless otherwise stated)
Authors, study
design level**; type of sporting activity
Hip/groin pain Control Diagnosis; duration
of symptoms
Comparisons between case and control;
SMD, MD or OR (95% confidence intervals)n Sex Age n Sex Age
Pain provocation tests
Jansen et al
30
Case–control
A, case=soccer(75%), running (12%), other (13%);
control=soccer (65%), running (13%), other (22%)
42 M 26±8 23 M 24±5 ARGP >6 weeks ADD squeeze test*, active straight leg raise*
Taylor et al
53
Cross-sectional cohort
P, AFL 15 M 17±1 218 M 16±1 Hip or groin injury, ND ADD squeeze OR=3.47 (0.9–12.9)
Mens et al
36
Case–control
A, case=soccer(70%), tennis (11%), other (19%),
control= soccer(70%), tennis (9%), other (21%)
38 M 31 38 M 32 Groin pain >1 month Active straight leg raise OR=56.64 (3.3–980.1), pelvic belt
OR=187.21 (10.8–3257.8)6F 28–35†6F30–35†
Verrall et al
16
Cross-sectional cohort
P, AFL 47 M ND 42 M ND Chronic groin injury
>6 weeks
ADD squeeze OR=5.02 (1.7–15.1), single adductor
OR=4.03 (1.2–13.5), bilateral adductor OR=24.76 (5.4–114.6)
Range of motion
Nevin and Delahunt
5
Case–control
ND, Gaelic football 18 M 24±3 18 M 24±4 ARGP >6 weeks IR=−0.82 (−1.5 to −0.1)*; SMD
ER=−0.57 (−1.2–0.1)*; SMD
BKFO=0.9 (0.2–1.6)*; SMD
Taylor et al
53
Cross-sectional cohort
P, AFL 15 M 17±1 218 M 16±1 Hip or groin injury, ND IR=−0.37 (−0.9–0.2)*; SMD
ER=0.06 (−0.5, 0.6); SMD
Malliaras et al
15
Case–control
P, AFL 10 M 17±2 19 M 17±1 ARGP >6 weeks IR=−0.02 (−0.8–0.8); SMD
BKFO=0.56 (−0.2–1.4)*; SMD
ER=−0.17 (−0.9–0.6); SMD
Verrall et al
33
Cross-sectional cohort
P, AFL 47 M ND 42 M ND Chronic groin injury
>6 weeks
IR=−0.39 (−0.8–0); SMD
ER=−2.55 (−4.8–0.3); MD (degrees)
Siebenrock et al
35
Cross-sectional cohort
P, ice hockey 15 M 19 62 M 14 Hip pain within past
6 months
IR=−0.85 (−1.4 to −0.3)*; SMD
11–36†9–34†
Strength
Malliaras et al
15
Case–control
P, AFL 10 M 17±2 19 M 17±1 ARGP >6 weeks ADD squeeze strength=−0.73 (−1.5–0.1)*; SMD
ABD strength=−0.25 (−2–1.9); MD (N)
Mens et al
36
Case–control
A, case=soccer(70%), tennis (11%), other (19%),
control= soccer(70%), tennis (9%), other (21%)
38 M 31 38 M 32 Groin pain >1 month ADD squeeze strength=−2.31 (−2.9 to -1.8)*; SMD
6F 28–35†6F30–35†
Nevin and Delahunt
5
Case–control
ND, Gaelic football 18 M 24±3 18 M 24±4 ARGP >6 weeks ADD squeeze strength=−2.06 (−2.9 to −1.2)*; SMD
Jansen et al
30
Case–control
A, case=soccer(75%), running (12%), other (13%);
control=soccer (65%), running (13%), other (22%)
42 M 26±8 23 M 24±5 ARGP >6 weeks ADD squeeze strength=−0.54 (−1.06 to −0.02) *; SMD
Mohammad et al
51
Case–control
ND, soccer 20 M 20±4 20 M 21±3 Osteitis pubis, ND ABD=−8.52 (−24.5–7.5), MD (Nm/kg)
ADD=−0.24 (−17.4–7.6), MD (Nm/kg)
Flex=38.85 (21.4–56.3)*, MD (Nm/kg)
Ext=11.79 (−1.5–25), MD (Nm/kg)
Ratios; ADD/ABD=0.06 (−0.5–0.6), Flex/Ext=0.18 (−0.8–1.2)*
Continued
4 of 12 Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602
Review
Table 1 Continued
Authors, study
design level**; type of sporting activity
Hip/groin pain Control Diagnosis; duration
of symptoms
Comparisons between case and control;
SMD, MD or OR (95% confidence intervals)n Sex Age n Sex Age
Trunk muscle function
Cowan et al
31
Case–control
A and P, AFL 10 M 26±7 12 M 25±6 ARGP >6 weeks TA=−30 (−38.4 to −21.6)*, OE=4 (−6.1–14.1) MD’s (ms)
OI=−1.1 (−7.9–5.7), RA=3.5 (−2.9–9.9); MD’s (ms)
Sayed Mohammad
et al
50
Case–control
ND, soccer 25 M 20±4 25 M 21±3 Osteitis pubis, ND Abdominals conc=1.78 (−9–12.5), ecc=−37.24 (−44.5 to −30)*; MD’s (Nm/kg);
back conc=−81.99 (−96.9 to −67.1)*, ecc=9.24 (−1.8–20.3); MD’s (Nm/kg);
Ratio abdominals/back conc=0.41 (−0.1–0.9)*, ecc=−0.28 (−0.7–0.1)
Jansen et al
30
Case–control
A, case=soccer(75%), running (12%), other (13%);
control=soccer (65%), running (13%), other (22%)
42 M 26±8 23 M 24±5 ARGP >6 weeks TA thinner at rest in groin pain group* no significant difference; OI at rest, TA or OI
with tasks
Radiological
Besjakov et al
39
Case–control
case=ND, soccer (85%), other (15%); control=ND,ND 20 M 26 20 M age-matched Groin pain, >3 months Case; 9/20 slight, 9/20 intermediate, 2/20 advanced abnormalities.
Control; 3/20 none, 17/20 slight abnormalities of pubic bone on X-ray19–35†
Paajanen et al
40
Case–control
ND, case=soccer (81%), other (19%), control=soccer
(50%), ice hockey (50%)
14 M 30±8, 20 M 23±4 Osteitis pubis
>3 months
Pubic bone oedema OR=8.08 (0.9–74.6)
2 F 22±11
Verrall et al
32
Case–control
P, AFL players and umpires 52 M ND 54 M ND Osteitis pubis, ND Pubic bone oedema OR=8.10 (2.8–23.5)
Cunningham et al
38
Case–control
case=A and P, soccer; control=ND, soccer (50%), rowers
(50%)
95 M 27 100 ND 23 Osteitis pubis, Mean of
3 months
Pubic bone oedema OR=1936 (111–33 733)
Secondary cleft sign OR=1423 (83–24 384)5F 17–38†18–28†
Brennan et al
37
Case–control
case=ND, soccer (83%), and rugby (17%); control=A,
rowers
18 M 24 70 M Groin injury, Mean of
3 months
Secondary cleft sign OR=271 (14–5122)
24
19–32†17–34†
Siebenrock et al
35
Cross-sectional cohort
P, ice hockey 15 M 19 62 M 14 Hip pain within past 6
months
αAngle MD’s (degrees);
9o’clock=-1.8 (−3–0.4), 10 o’clock=−0.8 (−3.1–1.5),
11 o’clock=2.3 (−3.9–8.5), 12 o’clock=6.1(−1.1–13.3)*,
1o’clock=9.8 (2.2–17.4)*, 2 o’clock=9.2 (2.2–16.2)*,
3o’clock=1.7 (−2.5–5.9)
11–36†9–34†
Other
Bedi et al
52
Case–control
ND, ‘physically active’subjects 10 M 23±6 19 M 22±3 FAI, ND COMP=48.00 μg/L (−9.1–105.1)*; MD
CRP=2.4 mg/L (0.9–3.9)*; MD
*Statistically significant difference.
†Range.
**Level: A, amateur; AFL, Australian Rules Football; ND, not described; P, professional/elite.
ABD, Hip abduction; ADD, Hip adduction; ARGP, adductor related groin pain; BKFO, bent knee fall out; COMP, Cartilage oligomeric matrix protein; CRP, C reactive protein; ER, hip external rotation; Ext, hip extension; F, Female; FAI, femoroacetabular
impingement; Flex, hip flexion; IR, hip internal rotation; M, Male; MD, mean difference; N, Newton; OE, obliquus externus; OI, obliquus internus; RA, rectus abdominus; ROM, range of motion; SMD, standardised mean difference;
TA, transversus abdominus; US, ultrasound.
Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602 5 of 12
Review
pelvic belt test:
36
OR=187.21 (3.27–980.14), impingement
test:
35
OR=50.62 (11.3–226.73).
The active straight leg raise test was also examined in an add-
itional high-quality study,
30
but despite the authors finding a
statistically significant difference between the control and hip/
groin pain subjects for this test (p=0.001), the mean of the
control group was 0 (0–0) and for the hip/groin pain group this
was also 0 (0–4), consequently an OR could not be calculated.
Despite the high-diagnostic ORs for the single adductor, bilat-
eral adductor, active straight leg raise, pelvic belt, and impinge-
ment tests, the results demonstrated in single studies show that
there is currently limited evidence that these tests differentiate
between hip/groin pain athletes from those without pain.
Range of motion
Five studies examined hip range of motion, including the vari-
ables of hip internal and external rotation, and bent knee fall
out.
515333553
Hip internal rotation (IR) was measured in prone with
the hip in neutral flexion/extension in 3 high-quality studies
(figure 3).
51553
The meta-analysis revealed strong evidence that
hip IR range in prone is less in athletes with hip and groin pain
SMD=0.42 (0.01–0.83) than those without pain. The differ-
ence in range between the two groups equated to an average of
3.7° (1.1–6.3°) of reduced hip IR in the athletes with pain,
which represents a weak effect.
Hip IR was measured in supine with the hip and knee at 90°
flexion in 2 moderate quality studies.
33 35
Meta-analysis pro-
vided moderate evidence that hip IR range measured in supine
was less in athletes with hip/groin pain; SMD=0.58 (0.14–1.01)
figure 4. This moderate effect equated to an average of 3.83°
(0.31–7.75°) of reduced hip IR in the athletes with pain.
External rotation (ER) was measured in supine with the hip
in neutral flexion/extension in three high-quality studies,
51553
and in supine with the hip in 90° flexion in 1 moderate quality
study.
33
The data was pooled for the three studies with neutral
flexion/extension (figure 5). There was strong evidence that hip
ER range of motion did not differentiate hip/groin pain athletes
from those without pain; SMD=0.18 (−0.55 to 0.19). In the
single study
33
with hip ER measured in 90° flexion, a weak
effect size was present between the hip/groin pain group and
control groups; SMD=0.47 (0.04–0.89). This difference in
range equates to 2.55° (0.31–4.79°), and provided limited evi-
dence that reduced hip ER range measured in 90° flexion was
associated with hip/groin pain in athletes.
Bent knee fall out (BKFO) is a combined movement of hip
flexion, abduction and external rotation, and was examined in
two high-quality studies,
515
Meta-analysis was possible as iden-
tical measurement methods were used. There was strong evi-
dence that a higher score on bent knee fall out, representing
reduced range of motion for this test, differentiates athletes with
hip/groin pain from those without pain; SMD=0.75 (0.24–1.27)
figure 6. This moderate effect equates to 3.6 cm (1.3–5.8 cm).
Strength
Strength on the adductor squeeze test measured at 45° hip
flexion, was examined quantitatively in five studies.
515303653
Data were available for four of these studies, and the pooled
data (figure 7) demonstrated strong evidence that the presence of
hip/groin pain was associated with less strength on adductor
squeeze testing. The effect size was large; SMD=1.41 (0.44–2.37).
The magnitude of the difference between the case and
control groups varied between the studies as represented by the
high statistical heterogeneity I
2
=89%. Separating the data into
Table 2 Patient reported outcome measures (data presented as mean (SD) unless indicated)
Study PRO Control Case Control Case Control Case Control Case Control Case Control Case
Likert (0–10) Worst pain last week
Average pain last
week
Pain aggravating
activity Pain on running Functional limitation
Cowan et al
31
0 (0) 6 (2) 0 (0) 3 (2) 0 (0) 7 (2) 0 (0) 6 (2) 0 (0) 3 (1) ND ND
Mens et al
36
0 (0) 6 (3) ND ND ND ND ND ND ND ND ND ND
Jansen et al
30
ND ND ND ND ND ND ND ND 0
0–0†
7*
2–10†
ND ND
HAGOS (0–100) Pain Symptoms ADL S/R PA Quality of life
Nevin and Delahunt
5
99 (3) 72 (15)* 93 (8) 55 (168)* 97 (8) 68 (19)* 94 (7) 40 (22)* 97 (5) 22 (23)* 96 (6) 38 (19)*
HOOS (0–100) Pain Symptoms ADL S/R Quality of life
Bedi et al
52
100 (0) 78 (22)* 98 (2) 70 (30)* 100 (0) 82 (18)* 98 (2) 60 (40)* ND ND 100 (0) 60 (40)*
SF-12 (0–100)
Bedi et al
52
PCS 57 (3)‡44 (14)*
,
‡
MCS 56 (5)‡59 (6)‡
*p≤0.05.
†Range.
‡Data extracted from graph.
ADL, activities of daily living; HAGOS, Copenhagen hip and groin outcome score; HOOS, hip disability and osteoarthritis score; MCS, mental component summary; ND, not described; PA, physical activity; PCS, physical component summary; PRO, patient
reported outcomes; S/R, function, sports and recreational activities; SF-12, Short form (12th version).
6 of 12 Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602
Review
common measurement units, the standardised mean difference
between case and control equates to 49 mm Hg (12–85 mm Hg)
and 53N (24–83N).
One high quality study also examined isometric abduction
strength using a hand-held dynamometer, in supine with neutral
hip flexion/extension.
15
There was no difference between the
hip/groin pain group and the controls for either leg (p=0.71–
0.84). Another high-quality study used an isokinetic dynamom-
eter to compare hip abduction, adduction, flexion, and exten-
sion strength.
51
In this study, only hip flexion strength was
significantly different (higher) in the hip/groin pain group com-
pared with controls (p=0.028). Similarly, the ratio of hip
flexors/extensors was significantly higher in the hip/groin pain
group compared to the controls (p=0.02). Therefore, there is
limited evidence that when using an isokinetic dynamometer,
hip flexion strength is greater in hip/groin pain participants than
controls, but abduction, adduction and extension strength are
similar.
Trunk muscle function
Trunk muscle function was measured in three high-quality
studies,
30 31 50
Table 1. The methodologies and outcome mea-
sures were distinctly heterogeneous, precluding meta-analysis.
The first study investigated electromyography activity of trans-
versus abdominus, obliquus internus and externus and rectus
femoris during an active straight leg raise task.
31
The onset of
transversus abdominus activity relative to rectus femoris was
found to be delayed in the hip/groin pain group in comparison
to controls (p≤0.05). There was no significant difference
between the onset timing for the other muscles relative to rectus
femoris. Another study
30
used ultrasound measurements to
compare the thickness of tranversus abdominis and obliquus
internus (as a measure of muscle recruitment capacity) at rest,
and during both the active straight leg raise task and adductor
squeeze test. The hip/groin pain participants had a significantly
thinner transversus abdominis (p=0.015) compared to controls
when measured at rest, though no difference was found in obli-
quus internus thickness ( p≥0.05). During both the active
straight leg raise and adductor squeeze test, the thickness of
both muscles was not significantly different between groups
(p≥0.15).
Isokinetic dynamometry was used in another high-quality
study to examine abdominal and back extensor muscle
strength.
50
A significantly lower concentric back (p=0.001) and
eccentric abdominal (p=0.005) muscle strength, and signifi-
cantly greater concentric abdominal/back extensor ratio
(p=0.019) was found in the hip/groin pain group compared to
the control group. There were no significant between-group dif-
ferences found for eccentric back and concentric abdominal
muscle strength (p>0.05), or eccentric abdominal/back extensor
ratio (p>0.05). Although these 3 studies examined different
aspects of trunk muscle function, synthesis of these findings
showed strong evidence that trunk muscle function is altered in
athletes with hip/groin pain compared to athletes without pain.
Radiological
One low quality study used X-ray to examine the pubic symphy-
ses of athletes with hip/groin pain and those without pain.
39
A reliable grading system quantified the abnormalities, which
were present in all the hip/groin pain subjects (9/20 slight, 9/20
intermediate, 2/20 advanced). In contrast, the athletic control
subjects had either no (3/20) or slight (17/20) abnormalities
seen on X-ray. Another moderate quality study only reported
the radiographic findings in the hip/groin pain subjects and not
the control subjects.
37
Synthesising the data on X-ray investiga-
tions of the pubic symphysis, there is currently limited evidence
that X-ray findings differentiate athletes with hip/groin pain
from athletes without pain.
Figure 3 Forest plot: association between hip/groin pain and hip internal rotation range of motion measured with neutral flexion/extension.
Figure 4 Forest plot: association between hip/groin pain and hip internal rotation range of motion measured with 90° hip and knee flexion.
Figure 2 Forest plot demonstrating the odds ratio of pain with the adductor squeeze test.
Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602 7 of 12
Review
Three moderate quality studies examined pubic bone oedema
using MRI in athletes with hip/groin pain and controls.
32 38 40
Dichotomous data for the presence or absence of bone oedema
were extracted and pooled from these studies (figure 8).
The results indicated that there were high odds that participants
with bone oedema on MRI would be in the hip/groin pain
group with a large effect size; OR=41.63 (1.6–1096.60).
However, there was high heterogeneity demonstrated by this
pooled result (I
2
=88%), and significant sensitivity to the data
from the study of Cunningham et al
38
Figures 8 and 9. The
removal of this study data resulted in an OR of 8.1 (3.1–21.2)
for the presence of bone oedema in subjects with hip/groin
pain, representing moderate evidence, with a large effect size,
that bone oedema in the pubic symphysis differentiates athletes
with hip/groin pain from those without this pain.
The presence of the secondary cleft sign was also examined in
2 moderate quality studies
37 38
and the data were pooled for
this outcome measure (figure 10). Meta-analysis showed a
strong association between the presence of the secondary cleft
sign and hip/groin pain OR=638.8 (82.9–4925.5). Indeed,
there was an absence of this sign on pubic symphysis MRI
examination of 170 athletic controls. These 2 studies provide
moderate evidence that the presence of the secondary cleft sign
differentiates athletes with and without hip/groin pain.
Other abnormalities were reported by 4 MRI studies.
32 37 38 40
However, inconsistent methods of reporting and analysis of these
abnormalities precluded data synthesis.
One moderate quality cohort study investigated the radio-
logical signs of femoroacetabular impingement (FAI).
35
This
study used MRI of the hip to determine whether higher α
angles correlated with the presence of symptomatic hips.
Athletes with symptomatic hips were found to have significantly
higher αangles when measured at the 12, 1 and 2 o’clock posi-
tions (corresponding to the anterolateral head-neck junction)
(p<0.022), but not at the 9, 10, 11 or 3 o’clock positions
(p=0.181–0.602). This means that there is currently limited evi-
dence that the radiological signs of FAI differentiate athletes
with hip/groin pain from those without these symptoms.
Other outcome measures
Biomarkers of cartilage damage and inflammation circulating in
the blood were examined in one high-quality study,
52
Table 1.
The biomarkers examined were cartilage oligomeric matrix
protein (COMP) and C reactive protein (CRP). COMP is a con-
nective tissue extracellular matrix protein that is a marker of
cartilage turnover, and increased levels of COMP are associated
with joint inflammation and OA.
52
CRP is another biological
marker that is associated with inflammation. Athletes with
symptomatic FAI had a 24% increase (p=0.04) in circulating
levels of COMP and a 276% increase ( p<0.001) in circulating
levels of CRP. Therefore, there is limited evidence that the bio-
markers for cartilage degradation and inflammation are elevated
in athletic males with hip/groin pain compared to controls.
DISCUSSION
This review systematically identified factors for differentiating
athletes with or without hip/groin pain. Of the 17 studies
included for data synthesis, 10 were of high quality, 6 moderate
and 1 low quality. A total of 62 variables were examined, with
meta-analysis performed for 8 of these variables. There is strong
evidence that the following variables differentiate athletes with
hip/groin pain from those without: PROs, pain on adductor
squeeze test, hip IR, bent knee fall out, adductor squeeze
strength, and trunk muscle function. Hip IR range of motion
measured in flexion differentiates painful athletes with a larger
effect size than when hip IR is measured in neutral. There is
moderate evidence that the presence of pubic symphysis bone
oedema and the secondary cleft sign are more common in ath-
letes with hip/groin pain. There is limited evidence that hip ER
measured in flexion differentiates between athletes with and
without hip/groin pain, and strong evidence that this movement
did not differ when measured in neutral. The low number of
studies comparing athletes with hip/groin pain to those without
hip/groin pain, using the following outcome measures: pain
provocation tests (apart from the squeeze test), X-ray abnormal-
ities of the pubic symphysis, radiological features of FAI, and
biomarkers of cartilage degradation, means that currently there
is only limited evidence supporting the association of these
outcome measures with the presence of hip/groin pain. The
findings of this review do not, however, indicate how well each
of the various clinical and radiological tests can determine the
presence of individual diagnostic categories.
The PROs used in the included studies were inconsistent, pre-
cluding meta-analysis. Furthermore, in some case–control
studies, PROs were used to exclude symptomatic athletes from
control groups.
30 31 36
Impairments in PROs ranged from 0 to
55%, suggesting that further cross-sectional and cohort studies
should use valid, reliable and consistent PROs to enable compar-
isons between studies.
Figure 5 Forest plot: association between hip/groin pain and hip external rotation range of motion measured with neutral flexion/extension.
Figure 6 Forest plot: association between hip/groin pain and bent knee fall out range of motion.
8 of 12 Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602
Review
Pain provocation tests are used clinically to diagnose hip/groin
pain, and commonly to determine inclusion and exclusion
criteria in research studies. This makes examining their ability to
differentiate somewhat artificial in cases where assignment to
case or control group has used pain provocation tests. We found
one high-quality study that compared the ability of various pain
provocation tests, conducted by a blinded assessor, to differenti-
ate athletes with and without hip/groin pain.
16
Another high-
quality cohort study
53
examined pain on the adductor squeeze
test, making meta-analysis possible for this test only. An OR of
4.31 (1.86–10) was found on meta-analysis, providing strong
evidence, with a large effect size, that pain on the adductor
squeeze test differentiates athletes with and without current hip/
groin pain. The results of the meta-analysis do not, however,
measure the validity of this test to diagnose any specific individ-
ual entity of groin pain. The lack of studies that met the inclu-
sion criteria for this review means that only limited evidence
exists for the diagnostic potential of the single adductor, bilat-
eral adductor, active straight leg raise, pelvic belt, and impinge-
ment tests to differentiate athletes with groin pain.
Hip IR measured in 90° flexion was examined in two moder-
ate quality studies.
33 35
Meta-analysis found moderate evidence,
with a moderate effect size, that this movement is less in athletes
with hip/groin pain; SMD=0.58 (0.14–1.01). There was strong
evidence, with a small effect size, that IR measured in neutral
flexion/extension differentiates these groups; SMD=0.42 (0.01–
0.83). The actual difference between groups for both these
movements was 3.8 and 3.7°, respectively, which approximates
the reported measurement error.
15
The association between a
loss of hip IR and hip/groin pain has been proposed
54–56
previ-
ously, with several possible mechanisms discussed. Bony
impingement is one plausible mechanism and this review pro-
vides some support for this mechanism with one cohort study
in which the symptomatic group had clinical and radiological
features of FAI.
35
The reduced hip range of motion associated
with athletic groin pain has also been proposed to result from
pain, muscle spasm, or capsular scarring.
22 55
There was conflicting evidence for hip ER; limited evidence
that ER measured in 90° hip flexion does discriminate and
strong evidence that ER measured in neutral flexion/extension
does not discriminate between athletes with and without hip/
groin pain. It has been suggested that the neutral position of the
hip is more reflective of the functional position for the demands
of football.
15
The findings of our review suggest that measuring
IR and ER in hip flexion may have greater clinical utility in the
management of hip/groin pain.
The BKFO test has good intratester and intertester reliability
with a measurement error of 2–3 cm.
15
Meta-analysis of 2 high-
quality case–control studies
515
found that hip/groin pain
athletes had lower range of motion in this test by 3.6 cm
(1.3–5.8 cm), supporting its clinical utility. The predictive ability
of the BKFO test for the development of hip/groin pain has not
been examined and prospective cohort research is recommended.
Hip adduction strength is considered important in hip/groin
pain, and lower scores on the adductor squeeze test at 45°hip
flexion were observed in hip/groin pain athletes in a
meta-analysis of four high-quality case–control studies.
5153036
The magnitude of the difference between the pain/no pain
groups varied between the studies and there was high statistical
heterogeneity which cannot easily be explained. It is unlikely to
be due to the differing tools of measurement (sphygmomanom-
eter and hand-held dynamometer), as the studies with the most
similar results used one of each tool. The age, duration of symp-
toms, sport played and diagnostic criteria were also similar
between studies. Therefore, although the heterogeneity is unex-
plained, each study and the overall pooled result confirm the
clinical utility of the adductor squeeze test. Lower adductor
squeeze test values have been shown to precede the onset of
Figure 7 Forest plot: association between hip/groin pain and strength score for the adductor squeeze test.
Figure 8 Forest plot: association between hip/groin pain and presence of bone oedema on MRI.
Figure 9 Forest plot: association between hip/groin pain and presence of bone oedema on MRI following sensitivity analysis.
Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602 9 of 12
Review
groin pain in a small study of Australian rules footballers,
57
but
this finding is yet to be tested in other populations. The meas-
urement of adductor squeeze strength is, therefore, recom-
mended in the screening for hip/groin pain in athletes and also
to monitor the treatment response in athletes with current hip/
groin pain.
In single studies, other strength measures (isokinetic hip
extension, adduction and abduction, isometric hip abduction)
did not differentiate between hip/groin pain athletes and con-
trols.
15 51
There is limited evidence that hip flexion and hip
flexion/extension ratio did differentiate, with higher hip flexion
strength found in the hip/groin pain group.
51
Prospective
studies using varying methods of measurement have identified
lower adduction strength as predictive of athletes who develop
hip/groin pain.
3212326
Our systematic review, therefore, sug-
gests that further investigation with reliable, valid and consistent
measurement methods and instruments is required to determine
which measures of strength, apart from the adductor squeeze
test, differentiate athletes with and without hip/groin pain.
Trunk muscle function was examined in three high-quality
case–control studies
30 31 50
using diverse measurement methods,
table 1. Different aspects of trunk muscle function were evalu-
ated: onset timing of the abdominals, eccentric and concentric
abdominal and back strength, and abdominal muscle bulk at
rest and with activity. These studies provide strong evidence
that trunk muscle function is altered in hip/groin pain athletes
and we suggest that it should be assessed and addressed in
management. A randomised controlled trial of an exercise pro-
gramme that included exercises aimed to improve trunk muscle
function has also been shown to be successful for the manage-
ment of long-standing groin pain.
58 59
The cross-sectional
nature of the included studies means that it is unknown
whether the altered trunk muscle function precedes or results
from hip/groin pain. Future prospective studies can examine
this question.
Only one low quality study of pubic symphysis X-ray was
included in our review.
39
This study found more abnormalities
in the hip/groin pain athletes. However, there was no informa-
tion available on the activity type or level in the controls, and a
previous study found higher activity levels to be associated with
a greater incidence of X-ray abnormalities.
60
It is possible that
the observed abnormalities are a result of activity rather than
related to the presence of hip/groin pain. Therefore, there was
limited evidence to indicate that pubic symphysis X-ray differs
in athletes with hip/groin pain compared to athletic controls.
The utility for diagnosis and management of hip/groin pain in
the athlete is not yet established.
We found moderate evidence that pubic bone oedema differ-
entiates athletes with hip/groin pain from those without pain.
However, a prospective study of 19 elite junior soccer players
found pubic bone marrow oedema in 13 asymptomatic players
at baseline.
34
One retrospective study in this review found no
bone oedema in 100 controls,
38
including 50 soccer players.
The absence of bone oedema in the 50 soccer player controls
contradicts other studies of asymptomatic footballers in which
54–72% had oedema.
32 34 40
Similarly, there was moderate evi-
dence that the presence of a secondary cleft sign differentiates
hip/groin pain athletes from athletes without pain, with an
absence of this sign in 170 asymptomatic control subjects.
37 38
It is worth noting that both these studies were from the same
clinic and may contain the same data set of MRI, thus poten-
tially influencing these findings. Our review found moderate evi-
dence that the presence of bone oedema and the secondary cleft
sign on MRI can differentiate athletes with and without hip and
groin pain. However, research with more rigorous methodology
is required to better understand the clinical and prognostic sig-
nificance of these findings. A recent review of the radiological
findings in athletic groin pain also found that methodological
quality was lacking and a systematic approach was needed in
future research.
61
The presence of radiological signs of FAI in athletes was
examined in one moderate quality study
35
providing limited evi-
dence that these signs can differentiate athletes with hip/groin
pain. There are many studies suggesting that the radiological
features of FAI are highly prevalent in athletic popula-
tions,
41 42 62–64
and in athletes with hip/groin pain.
65 66
However, case–control, cross-sectional and prospective studies
that examine FAI in athletes are lacking. There are many
unanswered questions regarding the relationship between radio-
logical and clinical signs of FAI in athletes, and how these relate
to the development of hip/groin pain. Further research in well-
described groups is required to answer these questions.
Limitations
This systematic review used strict predefined inclusion criteria;
therefore, some studies in the field were not included due to
either low subject numbers or use of non-athletic controls. The
search strategy was comprehensive and included six languages;
however some studies may still have been missed with this strat-
egy. The results of this review are also limited by the current state
of the literature, with inconsistent methods of measurement used
in the assessment, management and prevention of hip/groin pain
in athletes. The current lack of cohort studies with large partici-
pant numbers also limits the quality of the data available for syn-
thesis in this review. Most of the athletes included had chronic
groin pain and therefore, the generalisability of these findings to
athletes with acute groin pain is unknown. Furthermore, the low
number of female participants included in the studies potentially
limits the applicability of the findings of this review to female ath-
letes. Only 7 included studies used blinded assessors, suggesting a
potential for bias in many of the studies. It is recommended that
future research include blinded assessors and female participants
where possible.
CONCLUSIONS
This systematic review identified and synthesised data from 17
studies, of which 10 were high quality. The following levels of
Figure 10 Forest plot: association between hip/groin pain and presence of secondary cleft sign.
10 of 12 Mosler AB, et al.Br J Sports Med 2015;49:810. doi:10.1136/bjsports-2015-094602
Review
evidence were found for various factors able to differentiate ath-
letes with and without hip/groin pain. Strong evidence for:
PROs, pain on the adductor squeeze test, hip IR, bent knee fall
out, adductor squeeze strength and altered trunk muscle func-
tion. Moderate evidence for: pubic bone oedema, secondary
cleft sign. Limited evidence for: pain provocation tests (other
than the adductor squeeze), hip ER in 90°flexion, X-ray abnor-
malities of the pubis, radiological features of FAI and biomar-
kers of cartilage degradation. There is strong evidence that hip
ER range of motion does not differentiate between these ath-
letes when measured in neutral flexion/extension.
PROs, pain and reduced strength on the adductor squeeze
test, reduced range of motion in internal rotation and bent knee
fall out are the outcome measures that best differentiate athletes
with hip/groin pain from those without pain.
What are the new findings?
There is strong evidence that the following factors differentiate
athletes with hip/groin pain from those without:
▸Patient-reported outcomes
▸Presence of pain on the adductor squeeze test
▸Reduced strength score on adductor squeeze test
▸Reduced range of motion in hip internal rotation and bent
knee fall out
▸Altered trunk muscle function.
There is moderate evidence that the following factors
differentiate athletes with hip/groin pain from those without:
▸Presence of pubic bone oedema and secondary cleft sign on
MRI.
How might this review impact on clinical practice in the
near future?
▸Provides clinicians with an overview of how well measures
commonly used in the screening, assessment and
management of athletes differentiate between those with
and without hip/groin pain.
▸Summarises the literature on radiological measures of
relevance to hip/groin pain in athletes.
Acknowledgements The authors would like to thank Wichor Bramer for his
assistance with the literature search for this study.
Contributors ABM, RA, AW and KMC planned the manuscript. All authors
contributed to the interpretation of the data, writing, editing and approval of the
manuscript.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Open Access This is an Open Access article distributed in accordance with the
Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work non-commercially,
and license their derivative works on different terms, provided the original work is
properly cited and the use is non-commercial. See: http://creativecommons.org/
licenses/by-nc/4.0/
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