In closed-chain knee extension, which bone rotates internally on the other?

In closed-chain knee extension, which bone rotates internally on the other?

• A. The femur internally rotates on the tibia during terminal knee extension
• B. The tibia internally rotates on the femur during terminal knee extension
• C. The patella externally rotates on the femur during extension
• D. The fibula externally rotates on the tibia during extension

Answer: (A)

In closed-chain knee extension, with the foot fixed, movement at the knee occurs as the femur rotates on the tibia to reach full extension. Specifically, the femur rotates internally on the tibia as you straighten the knee, creating the knee-locking position. This is the opposite of open-chain extension, where the tibia rotates externally on the femur. The patella changes its tracking with extension, but it isn’t described as rotating on the femur in this context, and the fibula’s rotation is minimal and not a primary driver of the knee extension mechanics.

In closed-chain knee extension, with the foot fixed, movement at the knee occurs as the femur rotates on the tibia to reach full extension. Specifically, the femur rotates internally on the tibia as you straighten the knee, creating the knee-locking position. This is the opposite of open-chain extension, where the tibia rotates externally on the femur. The patella changes its tracking with extension, but it isn’t described as rotating on the femur in this context, and the fibula’s rotation is minimal and not a primary driver of the knee extension mechanics.