Anatomy & Injury
Knee Valgus
Knee valgus is an inward collapse of the knee during weight-bearing movement, where the knee caves toward the midline of the body rather than tracking over the foot. It is most visible during squatting, landing from a jump, or changing direction. The term is often used interchangeably with “knock knee” in static posture, but in S&C the more important context is dynamic valgus: the collapsing inward of the knee under load or during high-speed movement, which is one of the most consistent mechanical risk factors for ACL injury.
Why it matters
Dynamic knee valgus during landing has been identified in biomechanical research as a primary mechanical predictor of ACL injury, particularly in female athletes. When the knee collapses inward during deceleration or landing, it creates a combined valgus and rotational stress on the ACL that can exceed its tensile strength in a single extreme event or accumulate as chronic stress over repeated exposures. S&C coaches who observe consistent valgus patterns in their athletes during squatting or landing have a clear intervention target that is well within their scope to address.
Common causes and corrections
Knee valgus typically reflects weakness or poor activation in the glutes and hip external rotators, limited ankle dorsiflexion that forces compensatory inward knee movement, or simply a lack of exposure to controlled single-leg and landing movement under load. The correction is rarely about cueing the knees outward during heavy lifts. It is about building the hip and glute strength to produce that alignment automatically, improving ankle mobility where it is restricted, and progressively loading landing and deceleration patterns with correct mechanics before exposing athletes to high-speed demands. Coaches who cue knee alignment without addressing the underlying strength deficit typically see temporary improvement that disappears under fatigue or load.
Related terms
ACL (Anterior Cruciate Ligament) · Posterior Chain · Mobility · Movement Screen · Plyometric Progression