Runner's knee is patellofemoral pain syndrome, a dull ache around or behind the kneecap that often starts gradually. Pain rises with running and stairs, stems from overuse and weak thigh muscles, and needs care if it lasts despite rest. It can affect one or both knees. Runners and active adolescents report it most, but prolonged knee bending can trigger aching in sedentary people too.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
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What does it feel like?
The pain is a dull ache in the front of the knee. It centers around or behind the kneecap and builds slowly over days or weeks.
It typically worsens with running, climbing or descending stairs, squatting, kneeling and jumping. Sitting a long time with bent knees also brings it on. Mayo Clinic describes this gradual onset and front-of-knee location in Mayo Clinic's overview of patellofemoral symptoms and causes.
Who gets it?
Runners, active adolescents and young adults report it most often. The pattern fits sports with repeated knee bending under load.
Sedentary people are not exempt. Long periods with knees bent can produce aching, stiffness, catching, grinding or crackling. Desk work, driving and movie sitting are common triggers.
Why does it start?
Causes are usually multifactorial rather than single. Common contributors are repetitive loading, sudden mileage or hill-training increases, weak quadriceps and hips, poor patellar tracking, excess weight, and prior dislocation, fracture or knee surgery.
The exact cause is often unclear for a given person. Diagnosis is therefore clinical, based on symptoms and exam. Imaging mainly excludes structural damage, arthritis or other knee pathology, as explained in the AAOS OrthoInfo guide to patellofemoral pain syndrome.
What helps recovery?
The strongest evidence supports nonsurgical care. Start with temporary rest or activity modification, ice, and NSAIDs if tolerated.
Then rebuild with progressive hip- and quadriceps-strengthening physical therapy. Add low-impact fitness to maintain conditioning. Check footwear and running gait, since correction reduces repeat overload.
When should you seek care?
Get prompt evaluation if pain persists despite rest, limits walking or daily movement, keeps returning, or requires ongoing physical therapy. Contact a doctor sooner if movement becomes difficult. Get urgent or same-day care for these red flags: Mayo Clinic lists these urgent knee symptoms in Mayo Clinic's knee-pain guidance.
- cannot bear weight after a knee injury
- knee locks and will not straighten
- sudden severe swelling after injury
- hot, red, swollen knee with fever, a possible emergency