An MCL sprain is most often caused by which mechanism?

• A. Hit to the lateral side of the knee
• B. Direct blow to the medial knee
• C. Twisting injury with the knee planted
• D. Hyperextension without contact

Answer: (A)

The key idea is that the MCL is stretched by a valgus force on the knee, meaning the knee is pushed inward and the ligament on the inside is stressed. The most common way this happens in sports is a hit to the outside (lateral) side of the knee, which pushes the knee inward and loads the MCL. That’s why a blow to the lateral knee is the best answer.

Twisting with the knee planted can injure the MCL, but this mechanism often comes with broader ligament involvement and isn’t the most typical single cause. Hyperextension without contact tends to threaten the ACL and other structures more than the MCL. A direct blow to the medial knee would not create the classic valgus stress that preferentially strains the MCL in most cases.