Knee Valgus / Tracking
frontal-plane hip–knee–ankle angle under load (≈180° = straight; lower = deviation).
Why this matters
Medial knee collapse (valgus) under load is a well-known driver of ACL and patellofemoral injury. It usually reflects hip-abductor / external-rotator weakness or foot/ankle setup rather than the knee itself.
What good looks like
The knee drives straight over the foot through the squat / landing / single-leg task — minimal side-to-side travel.
Common faults
- Knee caves inward (valgus) — strengthen hip abductors/external rotators; cue "knees over toes."
- Worsens under fatigue or single-leg load — re-test both.
Related
source · sports/performance/learn/knee_valgus.md