Unlocking of knee is caused by?
**Core Concept**
The unlocking of the knee joint is a complex process involving the coordinated action of various muscles and ligaments. It is essential for knee extension and weight-bearing activities. The unlocking of the knee is primarily facilitated by the quadriceps muscle group, particularly the rectus femoris and vastus lateralis.
**Why the Correct Answer is Right**
During knee extension, the quadriceps muscle contracts, causing the femur to rotate on the tibia. This rotation is facilitated by the patella, which acts as a pulley system, increasing the mechanical advantage of the quadriceps muscle. The contraction of the quadriceps muscle also helps to relax the hamstrings, which are the primary knee flexors. This relaxation allows the knee to extend freely, unlocking it for movement.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the gastrocnemius muscle primarily contributes to knee flexion, not extension.
**Option B:** This option is incorrect because the popliteus muscle is involved in knee rotation and unlocking, but it is not the primary muscle responsible for knee extension.
**Option C:** This option is incorrect because the tibialis anterior muscle primarily contributes to ankle dorsiflexion, not knee extension.
**Clinical Pearl / High-Yield Fact**
The quadriceps muscle is responsible for approximately 60% of the total knee extension force, making it the primary muscle group involved in knee extension and unlocking.
**Correct Answer:** C.