That nagging ache under or around your kneecap. It builds on a long run, flares on the stairs, lingers after sitting for too long at a desk. Some days it feels manageable; other days it stops you mid-session. If you have been told you have "runner's knee", or if this description sounds familiar even though no one has given it a name yet, you are in the right place. Patellofemoral pain syndrome (PFPS) is the most common cause of anterior knee pain and one of the most frequently seen presentations in sports physiotherapy. It affects runners disproportionately, accounting for nearly half of all running-related knee injuries, but it is by no means exclusive to them. Cyclists, hikers, gym goers, adolescent athletes, and desk workers who sit for long periods with loaded knees are all well-represented in the population that develops it. Understanding what is actually happening, and why the treatment approaches that are most commonly tried often fail to address the root cause, is the starting point for genuinely getting on top of it.
What Is the Patellofemoral Joint?
The patellofemoral joint is formed between the patella (kneecap) and the trochlear groove at the front of the femur (thigh bone). As you bend and straighten your knee, the patella glides up and down within this groove, a movement that allows the quadriceps muscle to generate force efficiently across the full range of knee motion. The joint is under significant load during everyday activities. Forces across the patellofemoral joint during level walking are roughly half your bodyweight. During stair climbing they reach two to three times bodyweight. During deep squatting or running they can exceed seven to eight times bodyweight. This cumulative loading, repeated across thousands of steps, pedal strokes, or repetitions, is the context in which patellofemoral pain develops.
What Is Actually Happening?
Patellofemoral pain is not simply inflammation of the kneecap. The condition is better understood as pain arising from the patellofemoral joint and its surrounding structures, including the subchondral bone, the synovium, the fat pad, and the retinacular tissue, when those structures are being stressed beyond their current tolerance. The underlying driver is almost always a mismatch between load and capacity: the patellofemoral joint is being asked to absorb forces that exceed what it can currently handle, either because the load has increased (training spikes, new activity, return from a period of inactivity) or because the capacity has decreased (muscle weakness, neuromuscular fatigue, movement pattern changes), or both. What makes PFPS clinically interesting, and frequently mismanaged, is that the source of excessive patellofemoral load is almost never local. The kneecap itself is not weak. The problem lies in how forces are being generated and controlled above and below the joint.
The Real Drivers: Hip, Quad, and Foot
Hip Weakness, The Most Important and Most Overlooked Factor
Strong evidence consistently identifies hip muscle weakness, particularly of the hip abductors and external rotators, as a central feature of patellofemoral pain. When the hip abductors (primarily gluteus medius) and external rotators fail to adequately control the femur during single-leg loading, the thigh collapses inward. This produces a dynamic valgus position, the knee dropping toward the midline, which alters the tracking of the patella within its groove and dramatically increases contact pressure on the lateral facet of the joint. Research using systematic review and meta-analysis has found strong evidence that hip external rotation and abduction strength is weaker in people with PFPS compared to uninjured controls. Electromyographic studies have also shown delayed onset of gluteus medius activity in people with PFPS during functional tasks, meaning the muscle is not only weaker but is activating too late to protect the joint during loading. This is why addressing hip strength is now considered a central component of PFPS rehabilitation rather than an optional add-on, and why programmes that focus only on the quadriceps consistently produce inferior results to those that address the proximal hip musculature alongside it.
Quadriceps Weakness and Vastus Medialis Control
Locally, quadriceps weakness, and specifically the relative underactivity of the vastus medialis oblique (VMO), the teardrop-shaped muscle on the inner aspect of the knee, contributes to altered patellar tracking. The patella is pulled laterally by the iliotibial band and the vastus lateralis; the VMO is the primary medial stabiliser that balances this pull. When the VMO is underactive or relatively weaker than the vastus lateralis, the patella tracks laterally rather than centrally within the groove, increasing lateral facet loading. Quadriceps strengthening is important in PFPS rehabilitation, but it is most effective when combined with hip strengthening, a finding supported across multiple randomised controlled trials. A purely local approach that strengthens the knee without addressing the proximal drivers leaves the root cause unresolved.
Foot and Ankle Mechanics
Below the knee, foot posture and ankle mobility also influence patellofemoral loading. Excessive foot pronation causes the tibia to rotate inward, which has an upward kinematic effect on the knee, contributing to the dynamic valgus pattern that overloads the patellofemoral joint. Limited ankle dorsiflexion is also a consistent risk factor, as restricted ankle mobility forces compensatory movement at the knee during activities like squatting, descending stairs, or running. These distal factors are not universally present in PFPS, but they are common enough to warrant assessment, particularly in those whose symptoms persist despite adequate hip and quadriceps strengthening.
Who Gets Patellofemoral Pain?
PFPS has a general population prevalence of approximately 22.7%, making it genuinely common rather than a niche sports injury. It affects women more frequently than men, a pattern linked to differences in hip width, femoral geometry, and the greater dynamic valgus tendency that these anatomical features produce during loading. Runners are particularly affected, with PFPS accounting for nearly half of running-related knee injuries. Beyond runners, it is common in:
- Cyclists, particularly those with poor bike fit causing excessive knee load
- Adolescent athletes, especially during growth spurts, when muscle strength has not yet caught up with skeletal growth
- Military personnel, where rapid increases in walking and running load are common
- Desk workers, prolonged sitting with the knee in a loaded position can sensitise the joint, and the sudden transition to activity exacerbates this
- People who have recently increased their activity level, the training load spike is one of the most consistent precipitating factors
Why Does It Hurt More in Certain Situations?
The characteristic pain pattern of PFPS is closely linked to activities that increase patellofemoral joint load: Stairs (particularly descending), going downstairs generates very high patellofemoral forces because the knee is loaded in a flexed position while decelerating body weight. Descending is almost universally more painful than ascending. Prolonged sitting, the "movie sign" or "theatre sign" is a classic PFPS presentation: pain that develops after sitting for an extended period with the knees bent. The mechanism is thought to involve increased pressure on sensitised tissue in the retinaculum and fat pad, which builds as the joint remains in a static loaded position. Squatting and deep knee bending, loading the knee in flexion increases patellofemoral contact pressure significantly. Running, particularly at higher volumes or on downhill terrain, where the eccentric load through the quadriceps and the repetitive nature of the activity expose the joint to cumulative stress. After, not during, exercise, many people with PFPS notice that pain is worse in the hours following exercise rather than always during it. This post-activity flare reflects the inflammatory and sensitisation response to a loading session that exceeded the joint's current tolerance.
The Long-Term Risk: Why This Matters Beyond the Short Term
PFPS is not a benign, self-limiting condition. Research consistently shows poor long-term prognosis without appropriate treatment, a significant proportion of patients report ongoing symptoms at two to five year follow-up, and there is evidence that anterior knee pain may be a risk factor for early-onset patellofemoral osteoarthritis. This makes getting the management right early particularly important. Persistent pain leads to movement avoidance, muscle atrophy, altered loading patterns, and a progressive reduction in the capacity that was already insufficient, a self-perpetuating cycle that becomes harder to break the longer it is established.
What Actually Works: The Evidence for Treatment
Exercise, Hip and Knee Combined
Exercise is the most strongly evidence-based treatment for PFPS, and the evidence consistently supports a combined hip and knee approach over knee-only programmes. A systematic review of randomised controlled trials found that exercise programmes incorporating both hip strengthening (abductors, external rotators, extensors) and knee strengthening (quadriceps, particularly VMO) produced significantly better outcomes than quadriceps-focused programmes alone. The key exercises supported by the literature include: For the hip: clamshells, side-lying hip abduction, monster walks, single-leg squats, lateral step-ups, hip thrusts, and Romanian deadlifts targeting the gluteals and hip external rotators. For the knee: leg press, step-up and step-down exercises, terminal knee extensions, and progressive single-leg loading. Open kinetic chain exercises (knee extensions) have a role in PFPS rehabilitation, particularly in the early stages, because they allow isolated quadriceps loading without excessive patellofemoral joint compression. For the foot and ankle (where relevant): calf strengthening, ankle dorsiflexion mobility work, and foot intrinsic exercises where excessive pronation is a contributing factor. A progressive regime, typically two to four sets of ten or more repetitions, progressed over six weeks or more, is supported by the evidence and reflects the principle that meaningful strength gains require consistent, progressive loading over time.
Load Management
Alongside strengthening, managing the loads that are provoking symptoms is essential in the early and mid stages of rehabilitation. This does not mean stopping all activity, complete rest is neither necessary nor helpful, but it does mean identifying the specific activities and volumes that are driving the excessive patellofemoral load and modifying them while capacity is being built. For runners, this typically means temporarily reducing mileage, avoiding downhill running, and addressing training load spikes. A gradual, structured return to full volume is then implemented alongside the strengthening programme.
Patellar Taping and Bracing
Medially directed patellar taping (McConnell taping) has evidence for short-term pain reduction in PFPS, it is thought to act partly by altering patellar position and partly through neurophysiological pain modulation mechanisms. It is useful as an adjunct in the early stages of rehabilitation to allow exercise to be performed with less discomfort, but it does not address the underlying drivers and should not be relied upon as a standalone treatment. Knee braces with patellar cutouts or tracking supports can provide similar short-term symptomatic relief for some patients.
Foot Orthoses
For patients with significant foot pronation contributing to their symptoms, foot orthoses can reduce the rotational forces transmitted through the tibia to the knee. The evidence for orthoses in PFPS is modest but positive in a subset of patients, those with notable foot pronation are most likely to benefit.
What to Avoid
Prolonged rest without active rehabilitation is the most common management error in PFPS. The pain often does settle with rest, which creates the false impression that the problem has resolved. When activity is resumed, the underlying muscle weakness and movement pattern issues remain unaddressed, and symptoms predictably return, often worse than before, because deconditioning has further reduced the capacity that was already insufficient.
How IP Physio Can Help
We begin by establishing exactly what is driving your patellofemoral pain, because the same anterior knee pain can arise from different combinations of hip weakness, quadriceps deficit, movement pattern issues, and load management problems, and the programme needs to address what is actually present rather than a generic template. Our assessment includes objective strength testing using hand-held dynamometry to quantify hip and quadriceps strength deficits precisely, movement analysis to identify the dynamic valgus patterns and loading strategies that are stressing the patellofemoral joint, and a thorough load history to understand what has changed and what needs to be modified. From there, we build a structured exercise programme targeting the specific deficits identified, combined with practical load management guidance for your training or activity. We use objective strength testing at regular intervals to confirm the programme is producing the intended adaptations, because knowing your numbers tells us far more than how your knee feels on a given day. If you have been dealing with knee pain that keeps returning with every increase in activity, the approach you have tried so far may not have addressed the real drivers. Get in touch with us today and let's take a more systematic look at what is actually going on.
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