Runner's Knee: What Patellofemoral Pain Actually Is and How to Fix It

Patellofemoral pain syndrome (PFPS) — commonly called runner's knee — is the most prevalent running-related injury, accounting for approximately 17% of all running injuries. It presents as pain around or behind the kneecap, typically aggravated by running, squatting, descending stairs, and prolonged sitting with the knee bent. It affects runners and cyclists alike, but also plenty of people who have never run a step in their life.

Despite its frequency, patellofemoral pain is consistently undertreated — usually because the focus stays at the knee when the primary drivers are often a level higher, at the hip. Understanding why the patella becomes symptomatic requires looking at the whole lower-limb kinetic chain, not just the knee joint in isolation.

The Anatomy of Patellofemoral Pain

The patellofemoral joint is formed by the patella (kneecap) sitting within the trochlear groove of the femur. As the knee flexes, the patella is guided down into the groove; as it extends, it returns to a more proximal position. The direction of that tracking is governed by the balance of forces acting on the patella — primarily the quadriceps mechanism, the retinacular soft tissues (medial and lateral), and the position of the femur itself beneath the patella.

Crossley, Callaghan, and van Linschoten's 2016 clinical review in the BMJ describes PFPS as a condition characterised by increased stress at the patellofemoral joint — most commonly resulting from excessive lateral patellar loading — rather than a discrete structural lesion.¹ The pain is mediated by nociceptors in the subchondral bone and retinacular tissue, which become sensitised when joint stress chronically exceeds tissue tolerance. The key question is: what is driving that excess stress?

The Hip as the Primary Culprit

The most important paradigm shift in understanding patellofemoral pain came from the work of Christopher Powers and colleagues, who demonstrated through 3D motion analysis that the femur moves under the patella more than the patella moves on the femur during functional tasks. In people with patellofemoral pain, the femur tends to adduct (drop medially) and internally rotate during single-leg loading — and this femoral motion is driven primarily by weakness of the hip abductors (gluteus medius, gluteus minimus) and external rotators.²

When the femur adducts under a relatively static patella, the effective Q-angle increases — creating a greater lateral pull on the patella from the quadriceps mechanism, particularly the lateral portions of the vastus lateralis. The result is increased lateral patellofemoral joint stress and, over time, pain. This is why hip weakness is now understood as a primary contributor to patellofemoral pain rather than a secondary finding.

Four Contributing Factors

The 2018 International Consensus Statement

The most authoritative current guidance on patellofemoral pain comes from the 2018 consensus statement from the 5th International Patellofemoral Pain Research Retreat, authored by Collins, Barton, van Middelkoop, and colleagues, and published in the British Journal of Sports Medicine. The statement synthesised evidence from multiple systematic reviews and concluded that: exercise therapy — specifically hip and knee strengthening combined — is the recommended first-line treatment for patellofemoral pain, supported by strong evidence across multiple RCTs. It further recommended that orthoses, taping (specifically McConnell patellar taping), and gait retraining be considered as adjuncts to exercise rather than standalone treatments.⁴

The JOSPT Clinical Practice Guideline for PFPS (Willy et al., 2019) provides the same recommendation hierarchy: combined hip-and-knee exercise outperforms knee-only exercise, and exercise combined with education and load management outperforms either alone.⁵

What a Progressive Rehabilitation Programme Looks Like

Initial management focuses on reducing the pain stimulus — typically by modifying training load to a tolerable level, applying patellar taping to offload the lateral retinaculum acutely, and beginning hip abductor strengthening in non-provocative positions (sidelying hip abduction, clamshells, resistance band work). The goal in the first 2–4 weeks is to establish a base of hip strength while the knee pain settles.

As tolerance improves, exercise progresses to loaded, functional positions: step-downs, single-leg squats, and lunges that train the hip abductors and quadriceps together in the positions that mirror running and stair mechanics. Barton and colleagues' 2015 "best practice guide" in the British Journal of Sports Medicine described this progression as essential — early management without progression to higher-load, functional exercise rarely produces durable improvement.⁶

For runners, gait retraining — increasing step rate by approximately 10%, cueing anterior trunk lean, and addressing contralateral hip drop — can substantially reduce patellofemoral joint stress per stride without requiring speed or volume reduction. Willy and colleagues demonstrated that gait retraining produced clinically meaningful pain reductions in runners with PFPS that were maintained at 3-month follow-up.

Prognosis: Why You Should Not Ignore It

Patellofemoral pain is frequently dismissed as a minor inconvenience — people "run through it" until it becomes debilitating, or they simply stop running without addressing why it developed. The long-term data suggests this approach carries risk. A 2014 consensus statement in the British Journal of Sports Medicine noted that patellofemoral pain is associated with the later development of patellofemoral osteoarthritis, and that persistent, unmanaged PFPS is one of the modifiable risk factors for this outcome.⁷

The good news is that with appropriate management, outcomes are consistently good. The van der Heijden Cochrane review (2015) found that exercise produced significant improvements over control conditions in pain and function, and that benefits were maintained at 3–12 month follow-up. The structure of the programme matters — but more than structure, consistency does. Rehabilitation for patellofemoral pain works when people do the work.⁸