Hip Strength and Knee Valgus: What Research Actually Shows
Key insights: 60-second read
- Hip weakness may not be the main cause of knee valgus – a systematic review of 22 studies found no consistent relationship between hip abductor or external rotator strength and dynamic knee valgus in healthy people.
- Knee valgus is multi-factorial – while hip weakness is often blamed, stiff ankles, restricted hip rotation, and movement patterns can also cause the knee to cave in, which may be beyond the scope of this research.
- Assess the whole chain – ankle mobility, hip rotation, core stability, and movement control all need to be considered alongside hip strength.
- Don't assume hip weakness is the problem – strength alone may not change movement patterns if other restrictions are present.
If you have spent any time connected to the fitness or rehab world, you've probably heard the idea that weak hip muscles cause your knees to cave in during squats, lunges, or landing. This movement pattern – often called knee valgus – is commonly blamed on weakness of the hip abductors and external rotators.
But what does the research actually say? Is hip weakness really the main driver of knee valgus, or have we been missing the bigger picture?
A recent systematic review by Cashman and colleagues, published in The Knee, set out to answer this question. The researchers analysed 22 studies to determine whether there is a consistent relationship between hip abductor or external rotator strength and dynamic knee valgus in healthy people. Their findings may challenge some commonly held assumptions, but may also be looking at one piece of a broader puzzle.
On this page
1. Study Overview: How the Research Was Done
This was a systematic review – a research method that collects and analyses evidence from multiple studies to identify overall patterns.
The researchers identified 22 studies that met their inclusion criteria, spanning approximately 20 years of research on the proposed relationship between hip strength and dynamic knee valgus.
To be included, studies had to measure hip strength using dynamometry (either hand-held or isokinetic) and assess knee valgus using kinematic analysis. The researchers were specifically interested in the strength of the hip abductors and hip external rotators - those that biomechanically resist valgus knee forces.
2. What the Researchers Found
The results were surprisingly consistent across the studies – and they challenge the commonly held belief that hip weakness drives knee valgus.
Hip Abductor Strength
Fourteen studies examined the correlation between hip abductor strength and dynamic knee valgus. Of these:
- 12 studies found no statistically significant correlation.
- 2 studies supported the proposed relationship (weaker hips = more valgus).
- 2 studies found results in the opposite direction.
Hip External Rotator Strength
Twelve studies examined the correlation between hip external rotator strength and dynamic knee valgus:
- 8 studies found no statistically significant correlation.
- 2 studies supported the proposed relationship.
- 2 studies found results contrary to the hypothesis.
Key Finding: When researchers looked at the overall pattern across all 22 studies, 13 of the 22 studies did not find statistically significant evidence supporting the proposed relationship between weak hip muscles and greater knee valgus. Five studies supported the hypothesis, and four found results in the opposite direction.
The partial meta-analyses performed by the researchers also failed to achieve statistical significance. In other words, when compatible data from multiple studies were combined, no overall relationship between hip strength and knee valgus emerged.
3. A Physio's Perspective: Valgus Knee Isn't Just About Hip Weakness
If you've been told that your knees cave in because your hips are weak, this research may challenge that assumption. But does that mean hip strength is irrelevant? Not necessarily. It does, however, suggest that the picture is considerably more complicated than "weak hips cause knee valgus."
"Valgus knee is not a single-muscle problem. It is a movement strategy – and movement strategies are shaped by the entire chain, not just strength."
In my clinical experience, a knee that collapses inward during squats, lunges, or running is rarely caused by just one thing. Hip weakness may be a contributor, but several other factors can influence a valgus pattern.
What Else Can Cause Knee Valgus?
- Ankle Joint Stiffness: If your ankle lacks dorsiflexion (the ability to bend your ankle toward you), your body will always seek to find a way around it. It will always take the path of least resistance. It may turn your foot out or cave your knee in to find that extra range.
- Restricted Hip Rotation: The hip joint needs both internal and external rotation for smooth movement. If you lack rotational mobility, the knee may be forced to move inward to compensate for what's lacking at the hip.
- Movement Control and Coordination: The nervous system controls how we move. Sometimes knee valgus is simply a learned movement pattern that has become habitual, even when strength and mobility are adequate. Rather than strengthening the hip in isolation, we need to teach it how to act and support the knee from above.
- Core Stability: If the trunk and pelvis are not adequately controlled, the knee may cave in as part of a broader loss of control through the entire lower limb.
- Fatigue: Valgus may start to appear during fatigue, suggesting that endurance - not strength - is lacking.
"If your ankle is stiff, your knee has to go around it. If your hip lacks rotation, your knee has to go around that too. Valgus is often the result of compensation, not just weakness."
This is not to say that hip strength is irrelevant. But the research suggests that strengthening hip abductors and external rotators alone may not be sufficient to change movement patterns if other restrictions are present. A more comprehensive approach is needed.
4. What to Do Instead of Just Strengthening Hips
If you are dealing with knee valgus, here is a more comprehensive approach to consider:
- Assess ankle mobility. Check dorsiflexion range. If your ankle is stiff, address it with banded mobilisation and specific stretching.
- Assess hip rotation. Check both internal and external rotation. If movement is restricted, include rotational mobility work.
- Don't ignore the core. The pelvis needs to be controlled. If the trunk is unstable, the lower limb will compensate.
- Address movement patterns directly. Sometimes you need to teach the body what correct alignment feels like. Use mirrors, video feedback, or verbal cues during squats and other movements. A simple "feet straight", "knees out" squat prompt can help this over time.
- Consider the whole task. Knee valgus may only appear during certain tasks (single-leg stance, landing, fatigue). Identify the specific task and work on control in that context.
- Strengthen – but don't rely on it alone. Hip strength is still important for overall function. But do not assume it is the complete solution.
Key Takeaway: If you have been treating knee valgus with hip strengthening alone and not seeing results, the missing piece may be mobility – ankle or hip – or the movement pattern itself.
5. Study Limitations
As with any research, there are some limitations worth keeping in mind:
- Participants were healthy. The findings may not apply in the same way to people with existing pain, injury, or pathology.
- Study heterogeneity. The included studies varied in their methods, movement tasks, and measurement techniques, which limited the ability to combine data in meta-analysis.
- Correlation vs causation. The studies examined associations, not whether strengthening hip muscles actually changes knee valgus over time.
- Partial meta-analysis only. Not all data could be combined statistically due to methodological differences.
This research provides an important perspective on a commonly held belief. While hip weakness is often blamed for knee valgus, the evidence suggests that the relationship is not as straightforward as we once thought.
As a physiotherapist, I find that a valgus knee is usually a movement strategy shaped by the entire chain. It can come from ankle stiffness, restricted hip rotation, poor core control, or even just a learned movement pattern. Hip strength is one part of the puzzle – but it is rarely the whole picture.
If you are struggling with knee valgus or have been told that you just need to "strengthen your glutes," it is worth taking a step back and looking at the bigger picture. There may be other factors worth exploring.
- Grant
Frequently Asked Questions
Does this mean hip strength doesn't matter for knee valgus?
Not necessarily. The research suggests that hip weakness alone is not consistently associated with knee valgus in healthy people. However, this does not mean hip strength is irrelevant. Hip strength is still important for overall function and injury prevention, but it may not be the main driver of knee valgus that we once thought it was.
What are the other causes of dynamic knee valgus?
Knee valgus can be caused by ankle joint stiffness, restricted hip rotation, poor core stability, fatigue, or simply a learned movement pattern. The knee often caves in because it is compensating for restrictions elsewhere in the chain.
How do I know if my knee valgus is from hip weakness or something else?
A thorough assessment by a physiotherapist can help identify the underlying factors. Checking ankle mobility, hip rotation, core stability, and observing the movement pattern can provide clues. If you have been strengthening your hips and the valgus has not improved, it is worth looking at other areas.
Should I still do hip strengthening exercises?
Yes. Hip strength is still important for overall lower limb function. However, if your goal is to change a movement pattern like knee valgus, you may need to also address mobility restrictions and movement control alongside strengthening.
One key insight from this research
"A recent systematic review of 22 studies found no consistent relationship between hip abductor or external rotator strength and dynamic knee valgus in healthy people. Knee valgus is a multi-factorial movement pattern – ankle stiffness, hip rotation restrictions, and core control all play a role."
Reference
Cashman, G., White, C., Stephens, R., Hoggs-Johnson, S., & Kissel, J. (2026). The effect of hip abductor or external rotator strength on dynamic knee valgus in healthy subjects – a systematic review with partial meta-analysis. The Knee, 62, 104565. DOI: 10.1016/j.knee.2026.104565
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