Risk factors for patellofemoral pain: a systematic review and meta-analysis.

Patellofemoral pain, a common kind of kneecap-area pain, can appear in very different groups of people, from teenagers to military recruits to recreational runners, and researchers wanted to know which characteristics actually predict who develops it. This review pooled data from 18 prospective studies covering 4818 participants, of whom 483 went on to develop the condition, and compared commonly suspected risk factors such as body size, strength and alignment. The pooled results found that age, height, weight, body mass index, body fat and the Q angle (a measure of knee alignment) did not predict future patellofemoral pain. Quadriceps weakness emerged as a risk factor specifically in military recruits, while in adolescents greater hip abduction strength, rather than weakness, was linked to later pain, a finding that runs against typical assumptions.

The authors note the populations studied were distinct subgroups, and the evidence varies in strength across these different groups, which limits how broadly the findings can be applied.

If you've ever wondered why some people develop pain around the kneecap and others don't, this review looked at exactly that question, pulling together 18 studies that followed over 4800 people, mostly military recruits, adolescents and recreational runners, to see who went on to develop patellofemoral pain. The findings challenge some common assumptions.

Being older, taller, heavier, having more body fat, or having a particular knee alignment did not predict who developed this pain. In military recruits, weaker thigh muscles (specifically the quadriceps) were linked to a higher chance of developing pain later.

Interestingly, in adolescents, stronger hip muscles, not weaker ones, were associated with later pain, which is the opposite of what many might expect. Because these results come from different groups studied in different ways, with varying levels of confidence in the evidence, the findings can't be treated as a simple one-size-fits-all explanation for who develops this pain, and they don't tell us whether changing these factors would actually prevent it.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This review addresses what actually predicts future patellofemoral pain, informing how clinicians might frame risk discussions or screening priorities across different populations. Pooling 18 prospective studies (4818 participants, 483 incident cases) across three distinct subgroups, military recruits, adolescents and recreational runners, the authors found moderate to strong evidence that age, height, weight, BMI, body fat and Q angle were not predictive.

Quadriceps weakness normalised to BMI predicted future PFP in recruits (SMD -0.69, 95% CI -1.02 to -0.35), while in adolescents increased hip abduction strength, rather than weakness, was associated with later PFP (SMD 0.71, 95% CI 0.39 to 1.04), an unexpected subgroup finding. This sharpens the understanding that commonly assumed structural and anthropometric factors are not useful predictors, and that risk factors appear population-specific rather than universal. The subgroup-specific and sometimes counterintuitive hip strength finding in adolescents should be treated with caution given it rests on a smaller evidence base within one subgroup, and the review does not establish that modifying these factors would prevent patellofemoral pain.