In knee flexion, the ability to achieve tibial rotation is primarily due to laxity in which structures?

In knee flexion, the ability to achieve tibial rotation is primarily due to laxity in which structures?

• A. Cruciates
• B. Joint capsule
• C. Collateral ligaments
• D. Menisci

Answer: (C)

In knee flexion, tibial rotation occurs more readily when the ligaments on the sides of the knee (the collateral ligaments) are lax. These ligaments—one on the inner side and one on the outer side—primarily restrain rotational movement when the knee is bent. If they become lax, that rotational restraint is reduced, allowing the tibia to rotate relative to the femur during flexion. The joint capsule provides general stability, the menisci mainly improve congruence and load distribution, and the cruciate ligaments govern anterior-posterior translation and contribute to rotation in flexion, but the laxity most directly responsible for enabling tibial rotation in flexion is the collateral ligaments.

In knee flexion, tibial rotation occurs more readily when the ligaments on the sides of the knee (the collateral ligaments) are lax. These ligaments—one on the inner side and one on the outer side—primarily restrain rotational movement when the knee is bent. If they become lax, that rotational restraint is reduced, allowing the tibia to rotate relative to the femur during flexion. The joint capsule provides general stability, the menisci mainly improve congruence and load distribution, and the cruciate ligaments govern anterior-posterior translation and contribute to rotation in flexion, but the laxity most directly responsible for enabling tibial rotation in flexion is the collateral ligaments.