What type of movement will the MCL and LCL prevent?

What type of movement will the MCL and LCL prevent?

• A. Varus
• B. IR
• C. ER
• D. Valgus

Answer: (C)

Collateral ligaments stabilize the knee against sideways opening and help control rotation. The medial collateral ligament resists valgus stress (knee opening toward the outside on the medial side), while the lateral collateral ligament resists varus stress (knee opening toward the inside on the lateral side). In addition, both contribute to rotational stability by limiting external rotation of the tibia relative to the femur, especially with the knee flexed. Internal rotation is not their primary restraint. So, the movement these ligaments collectively help prevent is external rotation of the tibia (with valgus and varus being their direct side-to-side restraint roles).

Collateral ligaments stabilize the knee against sideways opening and help control rotation. The medial collateral ligament resists valgus stress (knee opening toward the outside on the medial side), while the lateral collateral ligament resists varus stress (knee opening toward the inside on the lateral side). In addition, both contribute to rotational stability by limiting external rotation of the tibia relative to the femur, especially with the knee flexed. Internal rotation is not their primary restraint. So, the movement these ligaments collectively help prevent is external rotation of the tibia (with valgus and varus being their direct side-to-side restraint roles).