Which of the following is not true about ACL injury?
**Core Concept**
The anterior cruciate ligament (ACL) is a crucial stabilizing ligament in the knee joint, responsible for preventing excessive forward movement of the tibia and rotational movements. ACL injuries are common in sports and activities that involve sudden stops, changes in direction, or landing from jumps.
**Why the Correct Answer is Right**
The ACL injury typically occurs due to a non-contact mechanism, such as a sudden pivot on a planted foot or a landing from a jump. This type of injury often results in a tear of the ligament, which can be partial or complete. The ACL is often injured in conjunction with other knee injuries, such as meniscal tears or medial collateral ligament (MCL) injuries.
**Why Each Wrong Option is Incorrect**
**Option A:** ACL injuries are often associated with a "pop" or a audible sound at the time of injury, which is true. However, not all ACL injuries present with a audible sound.
**Option B:** A false statement would be that ACL injuries are always caused by contact. While contact can contribute to ACL injuries, many ACL injuries occur without contact, making this statement incorrect.
**Option C:** A false statement would be that ACL injuries are rare in sports. ACL injuries are actually common in sports that involve rapid changes of direction, such as soccer, basketball, and tennis, making this statement incorrect.
**Clinical Pearl / High-Yield Fact**
The Lachman test is a specific test used to diagnose ACL injuries, and it is considered more sensitive than the anterior drawer test. The Lachman test involves applying a valgus stress to the knee while it is in a partially flexed position, which helps to assess the integrity of the ACL.
**Correct Answer: B.**