Could deep posterolateral knee pain after downhill running be popliteus tendinitis or impingement?

Doctor’s answer

The popliteus is an important stabilizer that 'unlocks' the tibia's internal rotation at the start of knee flexion. During downhill running, trail running, or excessive foot pronation, the popliteus tendon repeatedly resists anterior tibial translation through eccentric contraction, easily leading to tendinitis or friction impingement at the femoral lateral condyle groove. It presents as posterolateral knee tenderness, worsened by descending stairs, and needs differentiation from lateral meniscus tears and iliotibial band syndrome. Management focuses on reducing downhill running volume, strengthening quadriceps eccentric strength, and arch support.

This content is for education. Diagnosis, treatment, and rehabilitation require an individual assessment by a sports medicine specialist.