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.
Frequently asked questions
What does runner's knee feel like?
Runner's knee presents as a dull, aching pain behind or around the kneecap. It worsens with stairs (especially descending), squatting, prolonged sitting with bent knees, and running — particularly downhill. The pain typically starts gradually over weeks of training, not suddenly. Some runners notice clicking or grinding sensations (crepitus), but these are often painless and do not necessarily mean structural damage.
Can I keep running with runner's knee?
Yes, in most cases — but reduce your volume by 30-50% and keep pain below 4/10 during and after runs. Complete rest usually makes runner's knee worse, not better, because the underlying hip and quad weakness does not resolve without loading. Run on flat surfaces only (no downhills, no stairs) and pair reduced running with daily hip strengthening exercises. Stop immediately if pain spikes above 5/10 or lasts more than 2 hours after the run.
How long does runner's knee take to heal?
Most runners see significant improvement within 4-6 weeks of consistent daily hip and quad strengthening combined with reduced running volume. Full resolution typically takes 6-12 weeks. Runners who skip the strengthening work (just rest until pain goes) see recurrence rates above 40%. The pain fading is not the same as the underlying weakness being fixed — continue exercises for at least 8 weeks after pain resolves.
What's the best exercise for runner's knee?
Hip abductor strengthening, specifically the gluteus medius. Clamshells (3x15), side-lying hip abduction (3x12), single-leg squats to a chair (3x10), and lateral step-downs (3x10) are the evidence-based gold standard. Wall sits (3x30 seconds) strengthen the quadriceps. Do these daily for 4-6 weeks, then 3 times per week indefinitely as prevention.
Is runner's knee the same as patellar tendonitis?
No. Runner's knee (patellofemoral pain syndrome) is pain behind or around the kneecap. Patellar tendonitis (jumper's knee) is pain below the kneecap at the top of the patellar tendon. The treatment for tendonitis is heavy slow resistance loading of the tendon; the treatment for runner's knee is hip and quad strengthening. Misidentifying one for the other leads to ineffective rehab.
Should I use a knee brace or patellar strap for runner's knee?
Bracing can reduce pain during activity but does not address the underlying hip weakness causing the problem. Use a patellar strap or Cho-Pat-style band only as a short-term aid while you complete the strengthening protocol — not as a long-term solution. Over-reliance on bracing can delay the hip and quad strengthening that actually resolves the condition.
Can I run on a treadmill with runner's knee?
Treadmill running with a 1-2% incline is usually gentler on patellofemoral pain than road running because it removes downhill sections entirely and the belt surface is softer than concrete. Avoid setting the treadmill to 0% or negative grade (decline simulation), which replicates downhill loading. Keep sessions under 30 minutes initially and monitor pain for 24 hours after.
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.