The most sensitive manual test for an ACL tear.
The Lachman test is a manual special test used to assess the integrity of the anterior cruciate ligament by checking how much the tibia translates forward on the femur when the knee is held near 20 to 30 degrees of flexion. The examiner grades both the amount of anterior displacement and, just as importantly, the character of the end-point, whether it feels firm or soft and mushy.
A soft or absent end-point with increased translation strongly raises suspicion of ACL rupture and shapes immediate decisions around imaging referral, bracing, and activity modification. Because it is regarded as the most sensitive clinical test for this injury, a clearly positive Lachman carries real weight in early diagnostic reasoning, often before MRI confirmation is available.
With the patient supine and the knee flexed to roughly 20 to 30 degrees, the examiner stabilises the femur with one hand and grasps the proximal tibia with the other, applying a firm anterior pull while feeling for the amount of glide and the quality of the end-point. Comparison with the uninjured side is standard practice, since baseline laxity varies between individuals.
Sensitivity drops substantially in the acute setting when guarding, effusion, hamstring spasm, or pain limit relaxation, so a negative test soon after injury does not reliably exclude ACL rupture. Grading end-point quality is subjective and depends on examiner experience and hand size, and the test should be interpreted alongside history, other ligamentous tests, and imaging rather than in isolation.
This guide was auto-drafted and is pending editorial review.