Welcome to the 10th edition of the Learn.Physio Research Review!

Femoroacetabular Impingement

A research review by Learn.Physio

In this fortnight’s Research Reviews, we’ve got a couple of interesting papers that will help clinicians managing those with hip-related groin pain and/or femoroacetabular impingement (FAI).

The first article is an exciting paper that shows the benefit of pre-op physiotherapy strengthening of the hip muscles for those patients with a diagnosis of FAI. With plenty of research showing the benefits of pre-op strengthening for ACL injury, total knee replacements and total hip replacements; this was the first paper of its kind indicating the usefulness of strengthening prior to planned FAI surgery.

The second article revealed some useful information for those working with young dancers, and the role of differentiating between healthy dancers and those with hip-related groin pain. This data could be useful for screening purposes, or identifying those who need more rehab, or those who are back to a high performance standard following injury.

I sincerely hope you enjoy these 2 summaries and get something useful and practical out of them!


Femoroacetabular impingement (FAI) refers to hip pain associated with abnormal contact between the acetabulum of the pelvis and the femoral head-neck junction. It is commonly diagnosed in active, young adults and is thought to be a precursor to hip osteoarthritis (OA) over time.

Surgery is a treatment strategy for those with chronic FAI, with its intention to relieve structural impingement, and treat any residual injuries within the hip joint, thus improving pain-free ROM. Despite short term relief in symptoms with some patients (<1 year post-op), the long term prognosis is not great with 11-30% of patients requiring hip replacement surgery 5+ years down the track (Laude et al 2009 and Ng et al 2010).

One modifiable factor identified in the literature that is prevalent in those with FAI is hip muscle weakness; with the theory that persistent weakness of the hip muscles can lead to abnormal joint loading, leading to pain and dysfunction. No one muscle of the hip has been consistently been identified as a “weak” muscle with widespread hip muscle weakness in people with FAI being 11-28% lower than healthy controls (Casartelli et al 2011 & Guenther et al 2012).

Given that there is evidence to support 6 weeks of pre-op strengthening prior to total hip replacement surgery (Rooks et al 2006) but not yet FAI, the objectives of this study was to examine the immediate post-intervention changes of a pre-op hip strengthening exercise intervention on hip strength, pain and function in with those FAI.



Patients on a surgical waitlist for arthroscopic hip debridement surgery were screened for eligibility.
Inclusion criteria:

  • MRI evidence of FAI
  • Positive FADIR test
  • Self-reported anterior groin pain consistent with FAI
Exclusion criteria:
  • Evidence of hip OA on imaging
  • Cortisone injection into the hip within the last 1 month
  • Previous hip surgery
  • Significant lower limb injury other than FAI that would impair measurement of hip function or hip strength
  • History of osteonecrosis of the hip
Baseline testing was conducted prior to the 10-week strengthening intervention and performed again immediately after the intervention was completed looking at:
  • Isometric hip muscle strengthening in all 6 planes of hip movement (flexion, extension, abduction, adduction, internal rotation, and external rotation).
    • Hand-held dynamometry used to measure isometric strength
    • 5 sec maximal voluntary contractions
    • 3 reps for each movement, each limb
    • The largest force produced for each movement was converted to torque by multiplying the lever arm distance and then normalizing to body mass (Nm/kg).
  • Hip disability and osteoarthritis outcome score (HOOS)
  • Timed stair climb test
    • The time in seconds it takes to ascend 12 stairs as quickly as possible whilst contacting every stair
  • Global rating of change of their hip pain from baseline to post-intervention visit
    • Score ranged from -7 (a very great deal worse) to 7 (a very great deal better)

The 10-week, home-based hip strengthening intervention that progressively increased in its intensity and functionality over the 10 weeks. The program was divided into 3 phases and was encouraged to be carried out 4x per week, with each exercise being prescribed 3 sets of 10-12 reps per exercise, per session, and was consistent with the American College of Sports Medicine guidelines for strengthening. Resistance bands and weight cuffs were prescribed as required to ensure that exercise intensity remained high and challenging to the participants.

Link to full program here:


20 individuals (18 men, 2 females; mean age 29 years, BMI 24) underwent baseline testing. Participants reported hip pain for a mean of 53 months (approx. 4.5 years). All but 1 participant was available for post-intervention analysis.
7 participants demonstrated bilateral FAI, with 13 demonstrating unilateral FAI. For data analysis, in the event of bilateral FAI, the most painful and dysfunctional hip - the one scheduled for surgery - was considered to be the “affected hip”.
Isometric hip strength
  • Abduction, adduction and internal rotation all increased significantly at follow-up whereas the others did not.
  • All 5 HOOS sub-scales significantly increased at follow-up.
Timed Stair Climb
  • The amount of time it took to climb the 12 stairs decreased significantly.
Global rating of pain change
  • 52% reported that their pain had improved.
  • 42% reported no change.
  • 6% reported worse pain.
Overall, adherence to the intervention was good with 95% of allocated supervised sessions being attended by the participants. However, adherence to the independent home program was slightly lower at 79% completion rate. There was also a small amount of mild adverse events from the intervention that were recorded (post exercise soreness, lateral knee pain and low back stiffness – all resolving within 2 weeks) indicating that the program was well tolerated.

The objectives of this study were to examine the feasibility of a pre-op hip arthroscopy exercise intervention emphasizing hip strengthening in those with FAI; and the results certainly indicated that pre-op exercise rehab for FAI patients is a suitable option to help improve pain, function and symptoms, and allows researchers to explore further what role exercise rehab plays in those with FAI.
Key positives that should be highlighted from this study were:
  • Significant strength increases in hip abduction, adduction and internal rotation. It was interesting that flexion, extension, and external rotation didn’t increase; with the authors thinking that maybe these types of exercises weren’t challenging enough, or the intervention was not long enough? Nevertheless, strengthening appears to play a role here in helping patients improve their function, pain and quality of life.
  • The mean improvement in HOOS pain (9 points) and ADL sub-scale (10 points) scores indicated a clinically meaningful change.
  • Adherence to the 4x per week program was excellent with the independent home program still being conducted nearly 80% of the time (3.2x per week) which is much higher than 66% which has been previously reported in the literature (Linke et al 2011).
Despite these positive results, we do need to be conscious of some important limitations:
  • Absence of a control and/or placebo group makes it difficult to draw firm conclusions of the intervention’s true effectiveness.
  • Low rates of females (2 females) make it difficult to confidently generalize this to females presenting with FAI.
  • Based on this feasibility study, and despite the authors reporting that 5 participants cancelled their surgery since the intervention (and at 12 months post intervention had still not undergone surgery to the best of the authors knowledge), we don’t know yet whether this intervention leads to better long term post-op outcomes (at least 1-year post-op) compared to those that didn’t do the pre-op strengthening.


Despite a plethora of research in the benefits of pre-op strengthening for other lower limb conditions, this feasibility study was the first of its kind to explore the potential benefit of a 10-week pre-op hip strengthening program for those people with FAI.
It is without saying that a more robust, randomized controlled trial with long term follow-up is required in the future; but the results of this study are exciting and encouraging for patients and clinicians in that it showed that a 10 week hip-focused strengthening program that was progressive in nature, met the American College of Sports Medicine guidelines for strengthening and was conducted at least 3x per week resulted in significant improvements in hip adduction, abduction and internal rotation strength and improved function and quality of life – and importantly was very well tolerated with low rates of mild adverse events – in patients with FAI.


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The hip region is the second most injured area of the body amongst dancers, with FAI being one of the most common complaints. FAI occurs as the femoral head/neck region contacts the acetabulum of the pelvis resulting in increases stress to the joint capsule, synovium, and labrum of the hip joint. Despite the prevalence of hip pain amongst dancers, there is limited literature in the evaluation and management of FAI in dancers.

Screening of ROM, flexibility and strength to identify risk factors associated with injury to the spine and lower limbs of dancers is common amongst sports physio and sports medicine practitioners, however no screening measures to date have aided in the detection of FAI or other hip pathologies.
It is thought that these static measures (ROM, flexibility and strength) may be ineffective to assess the dynamic nature of dancing such as leaping and landing; thus, an ideal screening assessment should also include leaping, hopping and landing tasks.

Therefore the purpose of this study was to determine if dancers with clinical signs of FAI have differences in hip ROM, strength and hop test performance compared to healthy dancers; with the hypothesis being that healthy dancers would demonstrate greater strength, less ROM and significantly greater on hop tests than dancers with FAI.



Young female dancers aged between 18-22 who were participating in at least 8hrs per week of ballet, jazz, tap, lyrical or modern dance were recruited for this study.
Dancers were categorised into either “FAI group” or “healthy group” based on a combination of subjective and clinical tests. Inclusion criteria into the “FAI group” were:

  • Subjective history of groin pain that was reproduced with flexion, adduction and internal rotation (FADIR) and flexion, abduction, external rotation (FABER) tests.

Dancers categorised in the healthy group reported no history of lumbar spine or lower extremity pain including hip pain who also had negative FADIR and FABER tests.
These criteria were selected based on previous research indicating excellent 97% sensitivity for the combination of negative FADIR and FABER tests for ruling out FAI (Tijssen et al 2016).

Outcome measures:

Hip pain during dance activity assessed via numeric pain rating scale (NPRS) and Hip Outcome Score Activities of Daily Living and Sport Scales were primary outcome measures
Passive ROM of the hip (flexion, external rotation and internal rotation) was assessed by a standard goniometer as per previous research by Holm et al (2000).
Strength of the hip musculature was assessed via isometric contractions as measured by a handheld dynamometer. Hip flexion, extension, abduction, adduction, internal rotation and external rotation were all assessed in a randomised fashion with 3 maximal efforts being performed for each strength test (30sec rest between each effort). The average of the 3 efforts for each strength test was used for data analysis.
Hop testing consisted of the medial triple hop test, lateral triple hop test and the timed cross-over hop test in randomised order. These hop tests have been previously used in a dancing population with hip pain that demonstrated excellent test-retest reliability (Kivlan et al 2013).
Each subject performed 6 trials for each hop test on each leg with a 30sec rest between trials with the average of the last 3 hop tests for each leg, and each test used for data analysis.


There were 15 dancers (ave age 19.6yrs) that volunteered for this study that met the inclusion criteria for FAI, and 13 dancers (ave age 18.9yrs that volunteered to be part of the healthy control group; with no significant differences between groups in regards to age, height and weight.

As anticipated, there were significant differences between groups for self-reported pain and fucntion with the “FAI group” having lower scores on the Hip Outcome Score Activities of Daily Living (85/100 vs 94/100) and Sport Scales (81/100 vs 94/100) and higher pain scores during dance activities than the healthy group (2.5/10 vs 0.8/10).

In regards to ROM, there was no significant differences in ROM values for flexion, interanl rotation or external rotation between the 2 groups.

For isometric strength, the only measure found to be signifcantly different between the “FAI group” and the “healthy group” was 24% lower isometric hip extension strength in the “FAI group” vs the “healthy group”.

For the hop tests, the medial and lateral hop test distances (mean 354cm and 294cm respetively) were significantly less in the “FAI group” compared to the the “healthy control group” (410cm and 344cm respectively).


There were 2 key findings from this paper that partially support the authors original hypothesis that can be of value to physiotherapists working with young female dancers and performers with hip-related groin pain – specifically it apears that young dancers with mild hip-related groin pain symptoms have 24% lower isometric hip extension strength and have lower medial and triple hop test performance (approx 50cm less on each hop test) than healthy controls.

This is all well and good to know, and can be very useful for screening purposes to then allow clinicians to then try to address these strength and power deficits with targeted rehab strategies to help improve their symptoms over time, but I’m going to be blunt here - there were a lot of limitations to this paper that we need to consider.

Firstly this wasn’t a prospective, randomised control trial which does naturally lower its level of evidence. Secondly, and what I consider to be a big flaw in the study, was that diagnosis of “FAI” was made purely on clinical assessment, and did not inlcude a raiological assessment of either X-ray or MRI. A positive FADIR test could indicate intra-articular pathology to the labrum or articular cartilage; not necessarily be suggestive of FAI. This is important to note as many as 35% of dancers have MRI evidence of intra-acrticular pathology of the hip joint and do not report pain (Duthon et al 2013). Without X-ray or MRI evidence of FAI, we would need to tread very carefully with labelling these dancers with FAI; with hip-related groin pain being a more appropriate description here.

Thirdly, and really importantly, the authors did not make it clear at all if both limbs were being used for data analysis. It can be assumed from the data collection that they gathered ROM, strength and hop test data on the symptomatic limb of the FAI group, but there was no indication what method they chose to select the test limb for the healthy group. Did they choose to test the dominant limb? Or simply left or right? Also it would also have been nice to get a hop test limb symmetry index for analysis too.

Finally these results on a young, elite female dancers need to be carefully considered and taking care when trying to generalise this data to males, older females or less exerienced, young female dancers.

Despite its limitations, there was some useful information that can be utilised here for sports physios and sports medicine practitioners working with elite junior female dancers, especially when it comes to musculosketal screening purposes. Mostly what this paper provides is useful normative data for healthy dancers, as the data used for “FAI” athletes is highly debateable.

By knowing what distances healthy dancers can hop, it will allow standards to be set for injured athletes to strive for during rehab so that they know they are back to a high performance standard. This is useful to know as absence of pain does not mean a return back to pre-injury level of sport, or high performance.
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Review 1: 

Guenther, J. R., Cochrane, C. K., Crossley, K. M., Gilbart, M. K., & Hunt, M. A. (2017). A Pre-Operative Exercise Intervention Can Be Safely Delivered to People with Femoroacetabular Impingement and Improve Clinical and Biomechanical Outcomes. Physiotherapy Canada. Physiotherapie Canada69(3), 204–211.

Laude F, Sariali E, Nogier A. Femoroacetabular impingement treatment using arthroscopy and anterior approach. Clin Orthop Relat Res. 2009;467(3):747–52. Medline:19089524 http://dx.doi.org/ 10.1007/s11999-008-0656-y.

Ng VY, Arora N, Best TM, et al. Efficacy of surgery for femoroacetabular impingement: a systematic review. Am J Sports Med. 2010;38(11):2337–45. Medline:20489213 http://dx.doi.org/ 10.1177/0363546510365530.
Casartelli NC, Maffiuletti NA, Item-Glatthorn JF, et al. Hip muscle weakness in patients with symptomatic femoroacetabular impingement. Osteoarthritis Cartilage. 2011;19(7):816–21. Medline:21515390

Guenther JR, Gilbart MK, Hunt MA. People with femoroacetabular impingement exhibit altered frontal and transverse plane strength, movement, and gait characteristics compared to those without impingement. Osteoarthritis Cartilage. 2012;20(Suppl 1):S103–4.

Rooks DS, Huang J, Bierbaum BE, et al. Effect of preoperative exercise on measures of functional status in men and women undergoing total hip and knee arthroplasty. Arthritis Rheum. 2006;55(5):700–8. Medline:17013852 http://dx.doi.org/10.1002/ art.22223

Linke SE, Gallo LC, Norman GJ. Attrition and adherence rates of sustained vs. intermittent exercise interventions. Ann Behav Med. 2011;42(2):197–209. Medline:21604068 http://dx.doi.org/10.1007/ s12160-011-9279-8

Review 2:


Tijssen M, van Cingel RE, de Visser E, Holmich P, Nijhuis-van der Sanden MW. Hip joint pathology: relationship between patient history, physical tests, and arthroscopy fi ndings in clinical practice. Scand J Med Sci Sports. 2016.

Holm I, Bolstad B, Lutken T, Ervik A, Rokkum M, Steen H. Reliability of goniometric measurements and visual estimates of hip ROM in patients with osteoarthrosis. Physiother Res Int. 2000;5(4):241-248.

Kivlan BR, Carcia CR, Clemente FR, Phelps AL, Martin RL. Reliability and validity of functional performance tests in dancers with hip dysfunction. Int J Sports Phys Ther. 2013;8(4):360-369.

Duthon VB, Charbonnier C, Kolo FC, et al. Correlation of clinical and magnetic resonance imaging fi ndings in hips of elite female ballet dancers. Arthroscopy. 2013;29(3):411-419.


Thanks for reading and staying up to date. I look forward to sharing more in the future.

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