False regarding anterior cruciate ligament tear is?
**Core Concept**
The anterior cruciate ligament (ACL) is a crucial ligament in the knee joint, responsible for stabilizing the tibia (shinbone) relative to the femur (thigh bone). The ACL plays a vital role in preventing excessive forward movement of the tibia.
**Why the Correct Answer is Right**
A tear in the ACL can occur due to a non-contact injury, such as a sudden stop or change of direction, which causes excessive stress on the ligament. This type of injury often results in a "pop" sound, followed by pain and swelling in the knee. The ACL can be torn in either its mid-substance or at its attachment points to the femur or tibia.
**Why Each Wrong Option is Incorrect**
**Option A:** The ACL is not primarily responsible for rotational stability of the knee. While it does contribute to rotational stability, this is not its primary function.
**Option B:** The ACL does not have a bursa surrounding it. Bursae are fluid-filled sacs that reduce friction between tendons and bones, but they are not associated with the ACL.
**Option C:** The ACL is not innervated by the posterior articular nerve. The ACL is actually innervated by the middle genicular artery, which provides it with a rich blood supply.
**Clinical Pearl / High-Yield Fact**
The "Lachman test" is a clinical examination used to diagnose ACL tears. This test involves applying a gentle force to the tibia while stabilizing the femur, and observing for excessive forward movement of the tibia.
**Correct Answer: A. The ACL is not primarily responsible for rotational stability of the knee.**