When a patient gets up from sitting position which of the following events takes place in his knee joint?: (A) Medial rotation of femur on a fixed tibia, (B) Lateral rotation of femur on a fixed tibia, (C) Medial rotation of tibia on a fixed femur, (D) Lateral rotation of tibia on a fixed femur
Answer is A. Physiological locking occurs in extension when the femur is internally (medially) rotated on a fixed tibia.
Locking is a mechanism that allows the knee to remain in the position of full extension as in standing without much muscular efforts and is caused by quadriceps femoris.