What anatomical movement involves 5 degrees of tibial external rotation during terminal knee extension?

• A. Screw home mechanism
• B. Knee flexion
• C. Hip abduction
• D. Shoulder rotation

Answer: (A)

The screw home mechanism describes the last few degrees of knee extension where there is a significant rotation of the tibia. During terminal knee extension, the femur rotates medially while the tibia rotates laterally; this results in approximately 5 degrees of external rotation of the tibia. This rotation is a critical component of achieving a stable knee joint position, allowing for weight-bearing and preventing injury when the knee is fully extended.

This mechanism is essential not only for enhancing the stability of the knee joint but also facilitates the proper alignment of the lower limb during movement and promotes effective force transmission through the leg. Understanding this movement is vital for professionals in athletic training and rehabilitation, as it can inform strategies for injury prevention and body mechanics during athletic activities.