Final answer:
The screw home mechanism pertains to the slight medial rotation of the femur at the tibiofemoral joint during full knee extension, allowing the knee to 'lock' into a stable position.
Step-by-step explanation:
The screw home mechanism is related to the rotational movement of the tibiofemoral joint in full extension. This mechanism involves a slight medial rotation of the femur as the knee reaches full extension. The tibiofemoral joints, consisting of the medial and lateral articulations between the femur and tibia, enable knee movements. During extension, the lateral femoral condyle completes its rolling action first due to its smaller size when compared to the medial condyle, resulting in the aforementioned slight medial rotation which locks the knee in its most stable, weight-bearing position. Conversely, flexion starts with a slight lateral rotation of the femur, allowing the knee to unlock and move freely.