In a patient with knee problems, which ligament is likely injured if Lachman and anterior drawer tests are positive?

• A. Lateral collateral ligament
• B. Medial meniscus
• C. Anterior cruciate ligament
• D. Patella tendon

Answer: (C)

The anterior cruciate ligament (ACL) plays a crucial role in stabilizing the knee, particularly in preventing anterior translation of the tibia relative to the femur. When a patient presents with knee issues and both the Lachman test and the anterior drawer test yield positive results, it strongly indicates an ACL injury.

The Lachman test specifically assesses the integrity of the ACL and is often considered more sensitive than the anterior drawer test, especially when performed on a flexed knee. A positive result demonstrates increased anterior translation of the tibia due to the laxity created by the compromised ligament. Similarly, the anterior drawer test evaluates the same mechanism by applying an anterior force on the proximal tibia. When both tests are positive, it strongly suggests that the ACL is damaged or ruptured.

The other structures listed, such as the lateral collateral ligament, medial meniscus, and patellar tendon, have different roles in knee stability and would not typically cause positive results on both the Lachman and anterior drawer tests in the event of injury. Understanding the specific tests associated with each ligament or structure is critical in accurately diagnosing and treating knee injuries, highlighting the centrality of the ACL in this context.