Unlocking of knee to allow flexion ?
**Core Concept**
The unlocking of the knee to allow flexion involves the relaxation of the ligaments and muscles around the knee joint, enabling the tibia to move forward on the femur. This movement is facilitated by the contraction of certain muscles and the relaxation of others.
**Why the Correct Answer is Right**
During knee flexion, the quadriceps muscles relax, allowing the patella to move downward. As a result, the tension on the ligaments decreases, and the tibia can move forward on the femur. This movement is also facilitated by the contraction of the hamstrings, which pull the tibia upward and forward. The popliteus muscle plays a crucial role in unlocking the knee by rotating the tibia laterally, allowing the femur to move forward.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the muscle or ligament responsible for unlocking the knee. While the quadriceps muscles do relax during knee flexion, they are not directly responsible for unlocking the knee.
**Option B:** This option is incorrect because it does not accurately describe the movement of the tibia during knee flexion. The tibia moves forward on the femur, not backward.
**Option C:** This option is incorrect because it does not specify the muscle or ligament responsible for unlocking the knee. While the hamstrings do contract during knee flexion, they are not directly responsible for unlocking the knee.
**Clinical Pearl / High-Yield Fact**
The popliteus muscle is responsible for unlocking the knee joint, allowing for flexion. This muscle is often overlooked in clinical examination, but it plays a crucial role in knee movement.
**Correct Answer: C. Hamstrings.**