Lachman test

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A Lachman test is a medical test used for examining the Anterior Cruciate Ligament (ACL) in the knee for patients where there is a suspicion of a torn ACL.

To do this, lay the patient supine on a bed. Put the patient's knee in about 20-30 degrees flexion. The examiner should place one hand behind the tibia and the other on the patient's thigh. It is important that the examiner's thumb be on the tibial tuberosity. On pulling anteriorly on the tibia, an intact ACL should prevent forward translational movement of the tibia on the femur ("firm endpoint").

Anterior translation of the tibia associated with a soft or a mushy endpoint indicates a positive test. More than about 2 mm of anterior translation compared to the uninvolved knee suggests a torn ACL ("soft endpoint"), as does 10 mm of total anterior translation. An instrument called a "KT-1000" can be used to determine the magnitude of movement in mm.

The Lachman test is recognized by most authorities as the most reliable and sensitive clinical test for the determination of anterior cruciate ligament integrity, superior to the Anterior Drawer test commonly used in the past.

This test is named after orthopaedic surgeon, John Lachman, M.D.