Introduction

Hip muscle strength is often reduced in people with femoroacetabular impingement, making exercise a suitable treatment option. However, many undergo surgery before participating in an exercise program. The current international consensus guideline recommends that the first-line treatment should be exercise-based and last at least 3 months. Yet, an evidence-based exercise treatment for femoroacetabular impingement has not been established to date. That is why the current study wanted to examine the feasibility of 3 months of Strength Training for Femoroacetabular Impingement

Methods

This feasibility study aimed to evaluate the safety and achievability of a 12-week strength training program in people with femoroacetabular impingement. Participants between 18 and 50 years who were diagnosed with femoroacetabular impingement syndrome, according to the Warwick agreement were eligible.

The diagnostic criteria according to Warwick include a triad of Symptoms, clinical signs, and imaging findings that must be present to diagnose FAI syndrome:

• Symptoms include motion-related or position-related pain in the hip or groin. Pain may also be felt in the back, buttock or thigh. In addition to pain, patients may also describe clicking, catching, locking, stiffness, restricted range of motion or giving way.
• Clinical signs may include: a hip impingement tests that reproduces the patient’s typical pain. The most commonly used test is flexion adduction internal rotation (FADIR), but it is sensitive but not specific. There is often a limited range of hip motion, typically restricted internal rotation in flexion.
• Diagnostic imaging from an anteroposterior radiograph of the pelvis and a lateral femoral neck view may reveal cam or pincer morphologies
  • CAM morphology: Alpha angle ≥ 55° on anterior-posterior radiograph
  • Pincer morphology: lateral center edge angle > 39° on anterior-posterior radiograph
• Symptoms of reduced function and hip pain that impair hip-related quality of life

The intervention consisted of a 12-week strengthening program and consisted of 7 supervised sessions and 29 home-based sessions. The exercises were based on previous evidence by Kemp et al. (2018) and the authors also added exercises based on their clinical expertise. The exercises included:

• Hip extension
• Hip adduction
• Hip abduction
• Hip flexion
• Squatting

These exercises progressed to become gradually harder throughout the program.

Patients were educated on the pathophysiology of femoroacetabular impingement and were informed about provoking hip positions like deep hip flexion and internal rotation. They were told to try to avoid these positions.

Feasibility of the study was measured as the number of completed strength training sessions, as reported in the patient’s training diary. From this information, adherence to the program was calculated, which was the outcome of interest. High adherence to the program was defined when more than 75% of the planned sessions were completed.

Secondary outcomes included the Copenhagen Hip and Groin Outcome Score (HAGOS), the International Hip Outcome Tool (iHOT-33), and the Hip Sports Activity Scale (HSAS). A questionnaire measuring the participant’s expectations and satisfaction concerning the intervention was also completed. Muscle strength was assessed using a fixated hand-held dynamometer. Stability and balance were measured with the Y-Balance test. A performance outcome included the single-leg hop for distance. A change of ≥15cm was considered clinically meaningful for the latter two (MCID).

Results

Fifteen patients were included in the study, eleven of them were female. Their average age was 38 years.

All fifteen completed the strength training program. The participants completed 69% of the strength training sessions. No adverse events were reported. Pain did not increase after the strength training sessions. Over the weeks of the strength training program, pre-training pain decreased by a mean of 10 points from the first two weeks to the last two weeks.

All but one participant progressed to more demanding levels of exercise.

No changes were seen in the secondary patient-reported outcomes. A small change in the Y-Balance test was observed, but this was below the threshold of clinically relevant difference. The single-leg hop for distance improved beyond the threshold of the MCID. The strength measurements indicated mean changes above the threshold of the minimally clinically important difference of 0.15 Nm/kg, but the lower bound of the confidence interval was below the threshold.

Questions and thoughts

The study’s completion rate was high. All subjects completed the trial and 96% of the strength training sessions were completed. The participants were positive about the strength training program. Despite the trial finding significant differences exceeding the minimally clinically important differences for hip strength and the single-leg hop for distance training, no significant differences were reported in the patient-reported outcomes. Moreover, 6 out of the 15 participants (40%) had surgery at the end of the training for femoroacetabular impingement. The study mentioned that after completing the 12-week training program, the recruiting surgeon was contacted to plan the future treatment strategy.

If participants didn’t improve after three months, surgery was an option. However, I find three months too short. Femoroacetabular impingement syndrome develops gradually from early adolescence due to mechanical impingement at the hip. Optimizing hip musculature and performance could offer better long-term symptom relief.

I bet that, if the recruiter of this study hadn’t been a surgeon, the flow of participants to surgery would have been less or at least, not at 3 months already. Femoroacetabular impingement syndrome is a condition characterized by the gradual development and progression of mechanical impingement in the hip joint, which often begins in early adolescence and worsens over the years. Despite the slow onset, it is generally expected that an exercise program can significantly alleviate symptoms. However, given the chronic nature of femoroacetabular impingement and the long-term effects on hip function, a brief intervention of only 3 months may not provide substantial benefits. It is essential to recognize the discrepancy between the gradual progression of femoroacetabular impingement and the expectation of rapid improvement from a relatively short exercise program. As such, I would advise someone to participate and try functional strength training for at least 6 to 12 months before considering surgery. Rather than seeing someone 2-3 times per week in a physiotherapy clinic, I’d invest in a solid exercise program with monthly follow-ups to gradually progress the exercises. In case after this long period, no subjective improvements are seen, only then I’d consider surgery.

Talk nerdy to me

Comparing the participants who went over to surgery to those who did not reveal that those who received surgery had worse patient-reported outcomes both before and after the training program.

The small sample size and the fact that the study intended to examine the feasibility of the strength training program for femoroacetabular impingement should be considered when interpreting the findings. It seems that a strength training program is safe and feasible. There was sufficient adherence, which is positive since only 7 sessions out of the 36 sessions in total were supervised.

Patient expectations may also be a factor to consider. Knowing that these participants were recruited from a specialized orthopedic clinic and that a surgeon decided on further treatment planning after 3 months, you can expect that these patients may be leaning toward surgery from the very beginning of the study. For example, suppose they expect that surgery will help with their symptoms and they consult a surgeon, but they are told to try conservative therapy for 3 months first. In that case, they might expect these three months to bridge the waiting period for surgery.

The components of the strength training program should be further studied since only 5 exercises were included in the trial. Although they were progressed, they were mostly hip-focused. It would be interesting to see whether exercises targeted at the core, knee, and functional or sport-specific movements would increase the patient-reported outcomes to a greater extent.

Despite the absence of changes in patient-reported outcomes, hip strength was significantly increased, beyond the threshold for clinically relevant improvements. If a trial of longer duration and with more than 5 hip exercises is conducted, we can consider the relevance of strengthening for femoroacetabular impingement. The paper by Wall et al. (2016) could provide a starting point for you.

Take home messages

This study examined the feasibility of a strengthening program for femoroacetabular impingement syndrome and revealed that it was safe and achievable. Secondary outcomes revealed that strength was significantly increased to a clinically relevant level. The pain did not increase due to the strengthening and decreased over time. A relevant number of participants went over to surgery after finishing the 12-week strengthening, but methodological decisions made by the authors may partly explain this. It would be necessary to further study the effectiveness of this strengthening program as a primary outcome measure and to include more than 5 hip-focused exercises.

Reference

Kierkegaard-Brøchner et al., Safety and feasibility of a physiotherapist-led strength-training program in patients with femoroacetabular impingement syndrome. JOSPT Open (2024)