**Question:** Not true about anterior cruciate ligament.

A. It is a synovial joint ligament
B. It is involved in passive movements only
C. It is essential for rotational movements
D. It is formed by the fusion of two or more bones

**Core Concept:** Anterior Cruciate Ligament (ACL) is a crucial stabilizing structure in the knee joint. It is a ligament, which connects the femur to the tibia, and serves as a part of the synovial joint. The ACL plays a significant role in maintaining joint stability and preventing excessive anterior-posterior displacement of the tibia on the femur.

**Why the Correct Answer is Right:** The correct answer (option C) highlights that the ACL is essential for controlling rotational movements in the knee joint. This is because it acts as a dynamic stabilizer, preventing excessive anterior-posterior translation and internal-external rotation.

**Why Each Wrong Option is Incorrect:**

A. Option A is incorrect as the ACL is a ligament, not a bone. Although it is located between the femur and tibia, ligaments are different from bones. Ligaments are connective tissues that connect bones and help maintain joint stability.

B. Option B is wrong because the ACL is involved in active and passive movements. It plays a crucial role in both stabilizing the knee during active movement and assisting in passive movement when the joint is being passively moved by another person.

D. Option D is incorrect as the ACL is not formed by the fusion of two or more bones. Unlike bones, ligaments are composed of connective tissue and connect bones, providing stability and limiting excessive movement.

**Clinical Pearl:** Understanding the role of the anterior cruciate ligament (ACL) is crucial for proper diagnosis and management of ACL injuries. ACL tears can lead to instability and instability-related complications, such as meniscus injury and early osteoarthritis. Early recognition and treatment of ACL injuries are essential for minimizing these complications and restoring the patient's functional capacity.