Ruptures of the anterior cruciate ligament (ACL) are highly correlated with which knee position?

• A. Varus position
• B. The valgus position, or knees caving in
• C. Hyperextension
• D. Internal rotation

Answer: (B)

Ruptures of the ACL are most strongly linked to a valgus knee position, where the knees collapse inward. In dynamic movements like landing or cutting, a valgus alignment creates a knee abduction moment that drives the thigh and shin into a misaligned position. This places excessive shear and tensile stress on the ACL as the ligament tries to resist anterior tibial translation combined with rotational forces. Although hyperextension or rotational components can contribute, the valgus collapse is the most common and predictive pattern for ACL injury, which is why it’s the best answer. This understanding also informs prevention, emphasizing training to maintain knee alignment and control valgus during high-load tasks.