Lachman test

The Lachman test is a clinical examination technique used to evaluate the integrity of the anterior cruciate ligament (ACL) in the knee. It is considered one of the most reliable and sensitive tests for diagnosing ACL injuries, particularly in the acute setting.

Procedure

The Lachman test is performed with the patient in a supine position. The examiner flexes the patient's knee to approximately 20 to 30 degrees. The examiner then stabilizes the distal femur with one hand while the other hand grasps the proximal tibia. A gentle anterior force is applied to the tibia to assess the amount of anterior translation relative to the femur.

Lachman test being performed

The test is considered positive if there is increased anterior translation of the tibia compared to the contralateral side, indicating a potential tear of the ACL. The quality of the endpoint is also assessed; a soft or absent endpoint suggests a complete tear.

Clinical Significance

The Lachman test is a critical component of the physical examination for suspected ACL injuries. It is often preferred over the anterior drawer test due to its higher sensitivity and specificity, especially in the acute phase of injury when muscle guarding may limit the effectiveness of other tests.

A positive Lachman test is highly suggestive of an ACL tear, but it should be interpreted in conjunction with other clinical findings and imaging studies, such as magnetic resonance imaging (MRI), to confirm the diagnosis.

Limitations

While the Lachman test is highly effective, it may be difficult to perform in patients with large thighs or in those who are unable to relax their muscles. In such cases, alternative tests or imaging may be necessary to assess the ACL.

Related pages

• Anterior cruciate ligament injury
• Knee examination
• Pivot shift test
• Anterior drawer test