The Lachman Test is a test performed by the clinician to test for laxity of the anterior cruciate ligament.
Assessing cruciate laxity with the Lachman test
With the patient lying on their back and the head supported, the knee is flexed to 20-30 degrees, and the patient encouraged to totally relax. One hand grasps the femur, while the other grasps the upper tibia with the fingers at the back of the tibia and the thumb in front. Attempt is made to displace the tibia in relation to the femur, feeling both for the degree of displacement and the firmness of the end point.
Accuracy of 3 Diagnostic Tests for Anterior Cruciate Ligament Tears. Ostrowski JA. J Athl Train. 2006; 41(1): 120–121.
Reliability of the anterior drawer test, the pivot shift test, and the Lachman test. Kim SJ and Kim HK. Clin Orthop Relat Res. 1995 Aug;(317):237-42.