Lachman Stress Test: The Gold Standard for ACL Tears

The Lachman Stress Test is widely regarded as the most reliable orthopedic special test for diagnosing an Anterior Cruciate Ligament (ACL) injury. It assesses the amount of anterior tibial translation and the quality of the end-point.

[Image of Lachman Test procedure]

1. Purpose

The primary purpose of the Lachman Test is to **test for** the integrity of the Anterior Cruciate Ligament (ACL). It is considered the most sensitive and specific clinical test for detecting an acute ACL tear.

2. How to Perform

1. The patient is positioned in supine (lying on their back) with the knee flexed to 20-30 degrees.
2. The examiner stabilizes the distal femur (thigh) with one hand (usually the non-dominant hand).
3. The examiner grasps the proximal tibia (shin) with the other hand.
4. The examiner applies a quick, firm anterior (forward) translation force to the tibia while stabilizing the femur.

3. Positive & Negative Sign

Positive Sign (Test is POSITIVE):
A positive test (indicating an ACL tear) is:

• Excessive anterior translation of the tibia compared to the uninjured side.
• A "soft" or "mushy" end-feel (lack of a solid stop), indicating the ligament is torn.

Negative Sign (Test is NEGATIVE):
A negative test is a distinct, firm end-feel (hard stop) with minimal translation, similar to the healthy knee.