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.
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.
To do this, lay the patient supine
on a bed. Put the patient's knee in about 20-30 degrees flexion
, also according to Bate's Guide to Physical Examination the leg should be externally rotated. 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
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.
This test is named after orthopaedic surgeon
, John Lachman, M.D.