Research Review By Dr. Jeff Muir©


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Date Posted:

May 2022

Study Title:

Femoroacetabular impingement syndrome and labral injuries: grading the evidence on diagnosis and non-operative treatment – a statement paper commissioned by the Danish Society of Sports Physical Therapy (DSSF)


Ishoi L, Nielsen MF, Krommes K, Husted RS, Holmich P, Pedersen LL & Thorborg K

Author's Affiliations:

Sports Orthopaedic Research Center–Copenhagen (SORC-C), Arthroscopic Center, Department of Orthopedic Surgery, Copenhagen University Hospital, Hvidovre Hospital, Hvidovre, Denmark; Physical Medicine & Rehabilitation Research – Copenhagen (PMR-C), Department of Orthopedic Surgery and Physical Therapy, Copenhagen University Hospital, Hvidovre, Denmark; Department of Clinical Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; Danish Society of Sports Physical Therapy, Odense, Denmark

Publication Information:

British Journal of Sports Medicine 2021; 55: 1301–1310. doi:10.1136/bjsports-2021-104060

Background Information:

Hip-related pain in younger patients can often be attributed to femoroacetabular impingement (FAI), acetabular dyplasia or cartilage/labral injury (1). Of these, FAI is the most common, defined biomechanically as impingement of the femoral neck on the acetabular rim, due to a cam and/or pincer morphology (2). Cam morphology involves a non-spherical femoral head abutting into the acetabulum, while the pincer variety refers to over-coverage of the acetabulum relative to the femoral head – both of these (or the mixed morphology) can lead to mechanical impingement of the hip joint.

Consensus guidelines on the diagnosis and treatment of FAI have recently been published (1, 2), although these guidelines did not rate the available evidence using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) (3) or QUADAS-2 (A Revised Tool for the Quality Assessment of Diagnostic Accuracy Studies for diagnostic studies) (4, 5) rating tools. Assessment with these tools has been completed for special tests for FAI syndrome (6) and when comparing operative and non-operative treatment options for FAI (7), but not for FAI in general.

To address this gap in the guidelines, these authors sought to systematically search the literature and provide guidance for the diagnosis and non-operative treatment of FAI to general practitioners.


57 studies were eligible for inclusion in the guideline review.

Domain 1: Diagnostic Tests & Clinical Information

6 systematic reviews and 26 observational studies identified a total of 23 clinical tests and 14 different forms of clinical information. Only commonly used tests were summarized in the guideline review, based on three categories: combined FAI syndrome/labral injuries, FAI syndrome alone and labral injuries alone.

Flexion Adduction Internal Rotation (FADIR) Test
Two meta-analyses reported in one systematic review using MRA and surgery as reference standards observed moderate to very low diagnostic effectiveness (LR+: 0.86–1.04 and LR−: 0.14–2.3; low to very low quality of evidence) for the FADIR test for diagnosis of FAI syndrome/labral injuries. For FAI syndrome, nine cohort studies observed high to very high effectiveness (LR+: 1.00–3.30 and LR−: 0.09–0.83; low to very low quality of evidence) while for isolated labral injuries, high to very high effectiveness was also noted (LR+: 1.00–2.30 and LR−: 0.06–0.76; very low quality of evidence).

Flexion Internal Rotation (FI-R) Test
For diagnosis of FAI syndrome, two cohort studies (n = 304) observed very low diagnostic effectiveness (LR+: 1.25–1.51 and LR−:0.68–0.73; moderate quality of evidence) with the FI-R test. For diagnosis of labral injuries, one meta-analysis and one additional study showed moderate to very low effectiveness (LR+: 1.10–1.28 and LR−: 0.15–0.23; very low quality of evidence).

Flexion Abduction External Rotation (FABER) Test
For diagnosis of combined FAI/labral injuries, three cohort studies observed very low diagnostic effectiveness (LR+: 0.73–1.10 and LR−: 0.72–2.20; low quality of evidence). Similar low to very low effectiveness was noted for diagnosis of FAI syndrome when using pain provocation (LR+: 0.79–0.87 and LR−: 1.21–1.14; moderate quality of evidence – 2 cohort studies) or restricted range of motion (LR+: 1.01–1.36 and LR−: 0.41–0.93; moderate quality of evidence) as positive indicators. For diagnosing labral injuries, low to very low effectiveness was observed (LR+: 1.70 and LR−: 0.78; very low quality of evidence – only one cohort with 18 subjects).

Internal Rotation in Neutral Hip Position:
For diagnosis of FAI syndrome, one cohort study (n = 63) showed internal rotation in hip neutral (with patient prone and knee bent 90°) was associated with very low to low effectiveness (LR+: 4.83 and LR−:0.76; low to moderate quality of evidence) when using reduced range of motion as a positive indicator for diagnosing FAI syndrome.

Domain 2: Treatment

11 systematic reviews and 14 RCTs were identified as providing data on treatment effectiveness.

Prescribed Physiotherapy vs. Operative Treatment:
Evidence indicates that operative treatment is associated with a small but significant effect on iHOT-33 (International Hip Outcome Tool-33) at 8-12 months for FAI syndrome (mean difference: 11.02 points, 95% CI 4.83 to 17.21, I2=43%, Hedges g=0.41) (moderate quality of evidence). Other evidence suggests a small and non-significant improvement in iHOT-33 at 12 months with operative treatment (mean difference: 6.3 points, 95% CI −6.1 to 18.7, Hedges g=0.23) (very low quality of evidence). For labral injury, one study in patients over 40 showed a medium effect and significant improvement in iHOT-33 at 12 months with operative treatment (mean difference: 12.11 points, 95% CI 3.27 to 20.96, Hedges g=0.61) (moderate quality of evidence).

Prescribed Physiotherapy vs. Passive Modalities, Stretching and/or Advice:
A medium and significant effect was noted with prescribed physiotherapy on patient-reported function and pain at 12-weeks for FAI syndrome treatment (Hedges g=0.66, 95% CI 0.09 to 1.23, I2=0%) (low quality of evidence). A small and significant effect was also noted in HOOS-sport (Hip Disability and Osteoarthritis Outcome Score) scores at 6-weeks, favouring physiotherapy for hip joint pain (mean difference: 9.4 points, 95% CI 0.1 to 18.8, Hedges g=0.46) (very low quality of evidence).

Comparison of Different Physiotherapy Interventions:
A large and significant effect on iHOT-33 at 8-weeks in favour of hip/core exercises vs. hip exercises alone was noted for FAI syndrome (mean difference: 25 points, 95% CI 11.44 to 39.96, Hedges g=1.14) (very low quality of evidence). A trivial and non-significant difference in HOOS-sport at 12-weeks was noted in favour of hip strengthening exercises over movement pattern treating for hip pain (mean difference: 3.69 points, 95% CI −4.36 to 11.74, Hedges g=0.19) (low quality of evidence). At 12-months, however, a medium but non-significant effect was noted favouring movement pattern training (mean difference: 9.70 points, 95% CI −2.19 to 21, Hedges g=0.59) (very low quality of evidence). Finally, home hip exercises were favoured (large but non-significant effect) over manual therapy and supervised physiotherapy when comparing HOOS-sport scores at 6-weeks (mean difference: 21.1 points, 95% CI −9.1 to 51.3, Hedges g=1.27) (very low quality of evidence).

Pre-Operative Physiotherapy vs. Massage Therapy:
A non-significant effect after 8 weeks of physiotherapy over massage therapy was reported in one study using the Non-Arthritic Hip Score (NAHS), although the mean difference values were not reported in the study.

Prescribed Post-Operative Physiotherapy vs. Advice:
A medium and significant effect was noted with prescribed physiotherapy over advice for FAI syndrome and hip-related pain using the iHOT-33 at 12-14 weeks follow-up (mean difference: 14.37 points, 95% CI 2.98 to 25.77, I2=0%, Hedges g=0.67) (low quality of evidence). At 24-weeks, a small and non-significant difference in iHOT-33 was noted favouring post-operative physiotherapy (mean difference: 7.1 points, 95% CI −5.5 to 19.6, Hedges g=0.38) (low quality of evidence).

Clinical Application & Conclusions:

Based on the available data, the authors concluded that, regarding diagnosis of FAI, restricted internal hip rotation in neutral (0°) hip flexion (with knee in 90° flexion – patient prone) was the best test to rule in FAI and a lack of pain with the FADIR test and a lack of restricted motion with the FABER test were best to rule out FAI. Regarding treatment, prescribed physiotherapy was superior to passive modalities, stretching and/or advice, although hip arthroscopy was the most effective treatment option overall. The authors appropriately caution, though, that the confidence intervals for most statistics were wide, suggesting that continued research on diagnosis/treatment may result in change to the conclusions made in this study.

Study Methods:

A group of researchers with varied backgrounds (physiotherapists, orthopaedic surgeons, sports science researchers) gathered evidence on the diagnosis and treatment of FAI, including studies focused on FAI, FAI syndrome, acetabular labral injuries, or any combination thereof.

Literature searches included Medline (PubMed), CENTRAL and Embase (Ovid) to July 2020 and updated in July 2021. Only studies published in English were eligible. Eligibility of studies were evaluated by 2 reviewers, with a 3rd available in cases of disagreement. Eligible studies ranged from systematic review/meta-analyses to observational studies examining diagnosis and systematic reviews or RCTs for the treatment of FAI. “Diagnostic” studies were those that compared diagnostic tests and/or clinical information. “Treatment” studies included those that compared different forms of non-operative treatment or compared non-operative with operative treatments. Relevant outcomes included the Copenhagen Hip and Groin Outcome Score (HAGOS) (8) and International Hip Outcome Tool-33 (iHOT-33) (9).

2 authors appraised each eligible study using the GRADE framework (10) and the QUADAS-2 tool (5), as well as the risk of bias for each study using the ROBIS tool (11).

For diagnostic studies, positive and negative likelihood ratios (LR+, LR-, respectively) were used, based on the following rankings: very low (LR+: 1 – 2; LR−: 0.5 – 1), low (LR+: > 2 – 5; LR−: 0.2 – < 0.5), moderate (LR+: > 5 – 10; LR−: 0.1 – < 0.2); high (LR+: > 10; LR−: < 0.1). For treatment studies, standardized effect sizes (Hedges g) were used (12). Hedges g values not provided in studies were calculated using Review Manager v5.3 or Excel. The magnitude of treatment effect was ranked as follows: trivial (g < 0.2), small (g ≥ 0.2), medium (g ≥ 0.5) and large (g ≥ 0.8).

Study Strengths / Weaknesses:

  • A comprehensive search strategy and firmly established eligibility criteria were employed.
  • Use of GRADE and QUADAS-2 tools to evaluate the quality of evidence.
  • Comprehensive approach including both diagnosis and treatment (operative and non-operative) provides excellent information for general practitioners.
  • Only including RCTs evaluating treatment excludes possibly helpful observational studies.
  • No studies on injection for hip-related pain were included.
  • Only 3 databases were used in the literature search.

Additional References:

  1. Reiman MP, Agricola R, Kemp JL. Consensus recommendations on the classification, definition and diagnostic criteria of hip-related pain in young and middle-aged active adults from the International Hip-related pain research network, Zurich 2018. Br J Sports Med (Published Online First: 20 January 2020).
  2. Griffin DR, Dickenson EJ, O’Donnell J, et al. The Warwick agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. Br J Sports Med 2016; 50: 1169–76.
  3. Schünemann H, Brożek J, Guyatt G. Handbook for grading the quality of evidence and the strength of recommendations using the grade approach, 2013.
  4. Sterne JAC, Savović J, Page MJ, et al. Rob 2: a revised tool for assessing risk of bias in randomised trials. BMJ 2019; 366: l4898.
  5. Whiting PF, Rutjes AWS, Westwood ME, et al. QUADAS-2: a revised tool for the quality assessment of diagnostic accuracy studies. Ann Intern Med 2011; 155: 529–36.
  6. Caliesch R, Sattelmayer M, Reichenbach S, et al. Diagnostic accuracy of clinical tests for CaM or pincer morphology in individuals with suspected FAI syndrome: a systematic review. BMJ Open Sport Exerc Med 2020; 6: e000772.
  7. Ferreira GE, O’Keeffe M, Maher CG, et al. The effectiveness of hip arthroscopic surgery for the treatment of femoroacetabular impingement syndrome: a systematic review and meta-analysis. J Sci Med Sport 2021; 24: 21–9.
  8. Thorborg K, Hölmich P, Christensen R, et al. The Copenhagen hip and groin outcome score (HAGOS): development and validation according to the COSMIN checklist. Br J Sports Med 2011; 45: 478–91.
  9. Mohtadi NGH, Griffin DR, Pedersen ME, et al. The development and validation of a self-administered quality-of-life outcome measure for young, active patients with symptomatic hip disease: the International hip outcome tool (iHOT-33). Arthroscopy 2012; 28: 595–610.
  10. Guyatt GH, Oxman AD, Vist G, et al. GRADE guidelines: 4. Rating the quality of evidence--study limitations (risk of bias). J Clin Epidemiol 2011; 64: 407–15.
  11. ROBIS: A new tool to assess risk of bias in systematic reviews was developed. - PubMed - NCBI. Available: https://www. ncbi. nlm. nih. gov/ pubmed/ 26092286[Accessed 12 Sep 2019].
  12. Chapter 6: choosing effect measures and computing estimates of effect. Available: /handbook/current/chapter-06 [Accessed 12 Dec 2020].

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