Lachman’s Test assess the anterior cruciate ligament (ACL) in the knee. The ACL is one of the major ligaments that stabilizes the knee joint, particularly against forward movement of the tibia relative to the femur. Lachman’s Test is specifically designed to detect abnormalities or laxity in the ACL. Here’s how it’s typically performed:
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How to Perform Lachman’s Test:
- Patient Positioning: The patient lies supine (on their back) on the examination table with their knee flexed to about 20-30 degrees.
- Stabilization: The examiner stabilizes the patient’s thigh with one hand to prevent movement of the femur.
- Testing: With the other hand, the examiner grasps the patient’s tibia near the joint line and attempts to move the tibia forward (anteriorly) relative to the femur. The examiner assesses the amount of anterior translation (forward movement) and the quality of the end feel.
Interpretation of Results:
- Positive Lachman’s Test: If there is excessive anterior translation of the tibia compared to the contralateral side or if there’s a soft or mushy end feel instead of a firm end feel, it may indicate a tear or laxity of the ACL. This finding suggests instability in the knee joint and is highly suggestive of an ACL injury.
- Negative Lachman’s Test: If there is minimal anterior translation and a firm end feel, it suggests that the ACL is intact and providing appropriate stability to the knee joint.
Purpose of Lachman’s Test:
- Detecting ACL Injuries: The primary purpose of Lachman’s Test is to identify injuries or laxity of the ACL. ACL injuries are common in sports-related activities and traumatic injuries and can result in instability and functional limitations of the knee joint.
- Clinical Assessment: Lachman’s Test is considered one of the most sensitive tests for detecting ACL injuries. It provides valuable information to clinicians for diagnosing ACL tears and determining the appropriate management, whether it’s conservative treatment, such as physical therapy, or surgical intervention, such as ACL reconstruction.
Lachman’s Test, along with other clinical tests and diagnostic imaging modalities like MRI, helps clinicians make informed decisions regarding the treatment and rehabilitation of patients with knee injuries.
