What does a positive Lachman Test indicate?

A positive Lachman Test is indicative of joint laxity and potential injury to the anterior cruciate ligament (ACL). This test is specifically designed to evaluate the integrity of the ACL by assessing how much anterior translation of the tibia occurs relative to the femur when a stress is applied.

When a practitioner performs the Lachman Test, they stabilize the femur with one hand while pulling the tibia forward with the other. A significant amount of movement of the tibia with respect to the femur in the absence of a firm endpoint suggests that the ACL may be compromised, indicating potential injury or tear. The presence of joint laxity observed during the test is crucial for clinicians to further investigate an ACL-related injury, which is a common occurrence in sports-related activities, particularly those involving sudden stops or changes in direction.

The correct interpretation of this test, which aligns with identifying both joint laxity and a potential ACL injury, helps guide subsequent diagnostic imaging and treatment strategies.