Runner's Knee (PFPS).
Patellofemoral pain syndrome — commonly called runner's knee — is the most prevalent running injury, affecting roughly 25% of recreational runners at some point. The pain presents as a dull ache behind or around the kneecap, worsened by stairs, squatting, and prolonged sitting. Despite its prevalence, it is one of the most treatable running injuries when addressed correctly.
Overview
Runner's knee is an umbrella term for pain arising from the patellofemoral joint — the interface between the kneecap (patella) and the femoral groove in the thigh bone. It is distinct from patellar tendinopathy (pain below the kneecap) and meniscal injuries (pain along the joint line), though all three can coexist in the same runner. Prevalence is highest in female runners, runners under 30 and runners who have recently increased downhill training or stair work. It accounts for approximately 25% of all running injury clinic presentations.
Causes and biomechanics
The primary biomechanical driver is weak hip abductors (gluteus medius), which allow the knee to collapse inward during the stance phase of running, increasing lateral patella tracking forces by up to 30%. Poor quadriceps control, particularly of the vastus medialis oblique (VMO), compounds the problem by failing to counterbalance the lateral pull of the vastus lateralis. Sudden increases in training volume, downhill running, hill repeats, stair training and excessive lunging are the most common triggers. Overpronation, worn-out shoes with collapsed medial support and high Q-angle (hip-to-knee angle) are contributing structural factors.
Symptoms
A dull, aching pain behind or around the kneecap that worsens with stairs (especially descending), squatting, lunging, and prolonged sitting with bent knees — known as the 'movie sign' or 'theatre sign.' Pain typically starts gradually and increases over weeks of continued running. Crepitus (clicking, grinding or popping sensations) may be present during knee flexion but is not always painful and does not necessarily indicate structural damage. Pain is usually bilateral but often worse on one side.
Treatment protocol
Reduce running volume by 30-50% — do not stop completely unless pain exceeds 4/10, as complete rest leads to deconditioning without addressing the underlying weakness. Ice the kneecap area after runs for 15 minutes. Begin daily hip and quad strengthening: clamshells (3x15), side-lying hip abduction (3x12), single-leg squats to a chair (3x10), wall sits (3x30 seconds), and lateral step-downs (3x10). Most runners see significant improvement within 4-6 weeks of consistent targeted rehabilitation performed daily.
Prevention
Maintain gluteus medius and quadriceps strength year-round with 2-3 strength sessions per week of 15-20 minutes each. Follow the 10% rule for weekly mileage increases. Avoid sudden spikes in hill, stair or downhill running volume. Replace running shoes every 500-800 km before midsole cushioning degrades significantly. Consider professional gait analysis and potentially custom orthotics if symptoms recur despite consistent strengthening. Single-leg balance exercises also improve proprioception and dynamic knee stability.
Return to running
Resume full training when you can run 30 minutes on flat terrain completely pain-free. Increase volume by no more than 10% per week and avoid steep downhills or cambered road surfaces for the first 4 weeks of return. Maintain hip and quad strength work 2-3 times per week indefinitely as long-term prevention — this is not optional, it is a permanent addition to your training. Recurrence rates are high (up to 40%) in runners who stop their rehabilitation exercises once symptoms resolve.
This article is for educational purposes only and does not constitute medical advice. If you are experiencing pain or injury, consult a qualified sports medicine physician or physiotherapist before modifying your training. Read our full medical disclaimer.
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