Patellofemoral pain
Evidence: moderate
Exercise therapy is the best-supported treatment, and combining hip with knee strengthening beats knee work alone for pain and function. The popular hip-weakness story needs care: weakness is reliably associated with the pain, but prospective evidence that it causes the pain is mixed, and some of it points the other way. Passive add-ons such as long-term taping earn little support.
Not medical advice
This is a general knowledge base, not medical or dietary advice. If you are injured, unwell or weighing up a supplement or a change to your diet, speak to a doctor, physiotherapist or registered dietitian who knows your situation.
Patellofemoral pain, commonly called runner’s knee, is the single most frequent diagnosis in running clinics. It belongs to the family of common overuse injuries. The pain sits around or behind the kneecap, where the patella tracks against the femur, and it is load-related: the joint is asked to absorb more than it can currently tolerate.
How it presents
The pain is diffuse rather than pinpoint. Runners describe an ache around the front of the knee, behind or to the sides of the kneecap, that is hard to localise to one spot. It is provoked by activities that load the patellofemoral joint in a bent-knee position: running downhill, descending or climbing stairs, squatting and deep knee bends. A characteristic feature is pain after prolonged sitting with the knee flexed, the so-called ‘theatre sign’, named for the discomfort of sitting through a film or a long journey (Crossley et al. 2016). The knee usually looks normal, without the swelling or locking that points to other joint problems.
A multifactorial problem
There is no single cause. The headline factor is load, too much running volume or intensity applied faster than the joint adapts, which is why the condition clusters in runners ramping up training. On top of that sit several contributing factors that vary between individuals: how the hip and trunk control the leg during the stance phase, knee alignment, and the strength and timing of the muscles around the hip and knee (Crossley et al. 2016). Because the picture is mixed, treatment works best when it addresses load and the whole limb rather than chasing one supposed culprit.
The hip-strength evidence
Hip strength is the most discussed contributing factor, and it is worth stating precisely. Cross-sectional studies repeatedly find that runners with patellofemoral pain have weaker hip abductors and external rotators than pain-free runners (Rathleff et al. 2014). That association is real and consistent. What it does not establish is direction. A systematic review and meta-analysis separating the cross-sectional from the prospective evidence found that, while the weakness-with-pain link is strong in cross-sectional data, the prospective studies showed no association between baseline isometric hip strength and the later development of the condition. The authors concluded that hip weakness may be a result of the pain rather than its cause (Rathleff et al. 2014).
The implication is narrow. It is safe to say hip weakness is frequently present alongside the pain, and that addressing it helps. It is not safe to say weakness reliably causes the pain, because the best study design for that question does not support the claim.
Association is not causation here
The hip weakness seen in runners with patellofemoral pain may be a consequence of the pain as much as a contributor to it (Rathleff et al. 2014). The good news is that this does not change the treatment: strengthening the hip helps either way.
Treatment: strengthen, and manage load
The best-supported treatment is exercise therapy, and the most useful finding is about what to strengthen. Combined hip and knee strengthening beats knee strengthening alone for both pain and function. The Manchester and Gold Coast international consensus statements place this combination at the top of the evidence (Crossley et al. 2016). Whatever the causal direction of the weakness, adding hip-focused work, abduction and external-rotation strengthening, to the usual knee exercises produces better outcomes. See strength training for runners for how to build this into a programme.
Alongside strengthening comes load management. Complete rest is rarely needed or helpful; the better route is to cut running volume to a level the knee tolerates, then rebuild gradually rather than returning to full mileage at once (Crossley et al. 2016). This is the same load-first logic that governs the other common overuse injuries and is set out in return to running.
Gait retraining: a modest, real role
Changing how the foot strikes the ground can lower the load the kneecap absorbs. Increasing step rate, or cadence, by roughly 5 to 10% is the best-evidenced tweak. A simulation study found that raising step rate to 110% of preferred reduced peak patellofemoral joint force by about 14%, mostly by cutting knee flexion (Lenhart et al. 2014). The clinical follow-through holds: a 10% step-rate increase improved running kinematics and reduced symptoms in runners with patellofemoral pain at four weeks and three months (Bramah et al. 2019). The effect is genuine but modest, and it works alongside strengthening and load management rather than replacing them; see biomechanics and gait.
What does not help much
Several popular measures are weaker than their reputation. Passive modalities, the ultrasound, electrotherapy and manual-only treatments used as the main intervention, do not match exercise therapy, which the consensus statements rank first (Crossley et al. 2016). Patellar taping can give short-term symptom relief that may help a runner get going with rehab, but it is not a standalone cure and the case for long-term taping is thin (Crossley et al. 2016). As with the other overuse injuries, the core remains the same: reduce load, build capacity with strengthening, then rebuild running gradually. For the general principles, see the basics and running injuries.