Anteromedial versus posterolateral hip musculature strengthening with dose- controlled in women with patellofemoral pain: a randomized controlled trial

Key Points

1. 46 women with patellofemoral pain were included in this RCT which compared strengthening the anteromedial hip muscles (adductors, flexors and internal rotators) with the posterolateral hip muscles (abductors, extensors and external rotators).
2. Both groups also completed a warm-up, stretches and knee strengthening exercises.
3. Pain intensity and function improved in both groups with no significant differences in primary outcome measures between the groups.

BACKGROUND & OBJECTIVE

Patellofemoral pain (PFP) is recognized as a multi-factorial condition but one where exercises to strengthen the hip and knee muscles can be beneficial (1). For the most part, hip exercises have tended to focus on the gluteal muscles which can be effective for improving pain and function, especially when combined with quadriceps strengthening (2). The exact mechanism of action for this is unclear and some studies show the addition of strength work on top of education and activity modification doesn’t significantly improve outcomes (3).

This raises some intriguing questions: does it actually matter which muscles are the target of our rehabilitation? Are there other hip muscles that we may benefit from strengthening? This study sought to explore this by comparing the effectiveness of strengthening the anteromedial hip muscles versus posterolateral hip strengthening.

Patellofemoral pain is recognized as a multi-factorial condition.

Assessment of each individual patient’s strength should help us identify which is a priority for their rehab.

METHODS

This randomized controlled trial recruited 52 women with PFP, 46 of which completed the study and all assessments. Participants were randomized to either the anteromedial hip strengthening group (AMHG) or the posterolateral hip strengthening group (PLHG).

Both groups performed a warm-up and stretches for the hamstrings, abductors, adductors, quadriceps and calf muscles, as well as squats and seated knee extension exercises for quadriceps strengthening. In addition to this, the PLHG performed hip abduction in side-lying, resisted clams and resisted hip external rotation, while the AMHG did hip adduction in side-lying, flex ring squeezes in side-lying and hip internal rotation against resistance. See the video for demonstration of these exercises.

Hip Strengthening Exercises

All strengthening exercises were prescribed as 3 sets of 8 to 12 reps at 60-80% RPE (rate of perceived exertion). Exercise sessions were supervised, had an average duration of 60 minutes and were repeated twice per week for 6 weeks.

The primary outcomes were pain intensity (on a numerical scale) and function assessed by the Anterior Knee Pain Scale at 6 weeks. Secondary outcome measures included isometric strength testing and dynamic knee valgus during a step-down test.

RESULTS

Both groups demonstrated improvements in pain and function, but there were no significant differences in the primary outcomes between the two groups (at the 6-week or 6-month stage). The PLHG reported pain intensity reducing from an average of 5.27 at baseline to 1.15 at 6 weeks. The AMHG had similar improvements from 5.04 at baseline to 0.57 at 6 weeks. Despite improvements in strength there was no significant change in dynamic knee valgus in either group.

LIMITATIONS

• This was a study on women with PFP so results may not be applicable to male patients.
• The intervention was multi-modal including stretching, knee strengthening and hip strengthening. It’s unclear which of these interventions may have resulted in the improvements reported.
• The lack of a true ‘wait and see’ control also makes it difficult to rule out natural history / improvement over time, or contextual effects of regular supervised exercise and interaction with therapists.

CLINICAL IMPLICATIONS

This is a relatively small RCT, so we need to be careful in applying its findings without careful consideration. The results suggest that we should consider strengthening the anteromedial hip muscles (flexors, adductors and internal rotators) in women with PFP, and adds to existing evidence suggesting that posterolateral hip strengthening is also effective. Assessment of each individual patient’s strength should help us identify which is a priority for their rehab.

A secondary finding is also noteworthy - strengthening didn’t appear to alter dynamic knee valgus during a step-down. This is in line with other research which has reported that strength work alone doesn’t tend to significantly alter movement patterns. For example, strengthening the gluteals wont usually result in decreased hip adduction movement.

Likewise, strengthening the adductors isn’t likely to increase hip adduction during function. If our goal is to alter movement patterns, the specific movement itself needs to be practiced with appropriate cues to achieve the movement goal.

A final thought is that the approach to strengthening with 3 sets of 8 to 12 reps at 60-80% RPE is in line with other research and may provide a fairly simple, clinically applicable approach to building strength in patients with PFP. As ever this approach needs to be adapted based on symptoms, goals and individual needs.

+STUDY REFERENCE

Almeida G, Rodrigues H, Coelho B, Rodrigues C, Lima P (2021) Anteromedial versus posterolateral hip musculature strengthening with dose-controlled in women with patellofemoral pain: A randomized controlled trial. Phys Ther Sport, 49,149-156.

SUPPORTING REFERENCE

1. Barton CJ, Lack S, emmings S, Tufail S, Morrissey D. The 'Best Practice Guide to Conservative Management of Patellofemoral Pain': incorporating level 1 evidence with expert clinical reasoning. Br J Sports Med. 2015 Jul;49(14):923-34. doi: 10.1136/ bjsports-2014-093637. Epub 2015 Feb 25. PMID: 25716151.
2. Lack S, Barton C, Sohan O, Crossley K, Morrissey D. Proximal muscle rehabilitation is effective for patellofemoral pain: a systematic review with meta-analysis. Br J Sports Med. 2015 Nov;49(21):1365-76. doi: 10.1136/bjsports-2015-094723. Epub 2015 Jul 14. PMID: 26175019.
3. Esculier JF, Bouyer LJ, Dubois B, Fremont P, Moore L, McFadyen B, Roy JS. Is combining gait retraining or an exercise programme with education better than education alone in treating runners with patellofemoral pain?A randomised clinical trial. Br J Sports Med. 2018 May;52(10):659-666. doi: 10.1136/bjsports-2016-096988. Epub 2017 May 5. PMID: 28476901.