Which combination of structures constitutes the major injury triad when the knee sustains a lateral impact?

Which combination of structures constitutes the major injury triad when the knee sustains a lateral impact?

• A. Medial collateral ligament, medial meniscus, and anterior cruciate ligament
• B. Lateral collateral ligament, lateral meniscus, and posterior cruciate ligament
• C. Medial collateral ligament, lateral meniscus, and posterior cruciate ligament
• D. Anterior cruciate ligament alone

Answer: (A)

When a knee is struck from the outside (lateral impact), the force tends to push the knee into valgus, stressing the structures on the inside. The major injury triad in this scenario is the medial collateral ligament, the medial meniscus, and the anterior cruciate ligament. The MCL is the primary restraint to valgus stress, so it commonly tears. The medial meniscus is tightly linked to the MCL and is often damaged when this complex is stressed, due to their close anatomical relationship. The ACL can be injured through rotational forces and anterior tibial translation that accompany the pivoting motion of the knee in this mechanism. The other options involve ligaments and menisci on the lateral side or an isolated ACL injury, which do not fit the typical valgus-driven pattern.

When a knee is struck from the outside (lateral impact), the force tends to push the knee into valgus, stressing the structures on the inside. The major injury triad in this scenario is the medial collateral ligament, the medial meniscus, and the anterior cruciate ligament. The MCL is the primary restraint to valgus stress, so it commonly tears. The medial meniscus is tightly linked to the MCL and is often damaged when this complex is stressed, due to their close anatomical relationship. The ACL can be injured through rotational forces and anterior tibial translation that accompany the pivoting motion of the knee in this mechanism. The other options involve ligaments and menisci on the lateral side or an isolated ACL injury, which do not fit the typical valgus-driven pattern.