Lachman's test is done with knee in____ degree of flexion

Ans. b (20). (Ref. Current orthopaedics, Chapter 4).LACHMAN TEST is the most sensitive test for ACL tears. It is done with the knee flexed at 20 degrees, stabilizing the distal femur with one hand and pulling forward on the proximal tibia with the other hand. With an intact ligament, minimal translation of the tibia occurs and a firm end point is felt. With a torn ACL, more translation is noted, and the end point is soft or mushy. The hamstring muscles must be relaxed during this maneuver to prevent false-negative findings. Comparison of the injured and uninjured knees is essential.Also Remember:Anterior Drawer TestIt is done with the knee at 90 degrees of flexion and is not as sensitive as the Lachman test but serves as an adjunct in the evaluation of ACL instability. With the patient supine and the knee flexed to 90 degrees (hip flexed to approximately 45 degrees), the foot is restrained by sitting on it, and the examiner's hands are placed around the proximal tibia. Then while the hamstrings are felt to relax and the tibia is pulled forward, the displacement and the endpoint are evaluated.Pivot shift test ( Losee Test)It demonstrates the instability associated with an ACL tear. As described by Losee, a valgus and internal rotation force is applied to the tibia. Starting at 45 degrees of flexion, the lateral tibial plateau is reduced. Extending the knee causes the lateral plateau to subluxate anteriorly with a thud at approx 20 degrees of flexion. It reduces quietly at full extension.Posterior Drawer TestThe posterior drawer test evaluates the integrity of the PCL. It is performed with posterior pressure on the proximal tibia with the knee flexed at 90 degrees. Normally, the tibial plateau is anterior to the femoral condyles, and a step-off to the tibia is palpated when the thumb is slid down the femoral condyles. With a PCL injury, sagging of the tibial plateau may be appreciated, and no step-off is palpated. An associated contusion on the anterior tibia suggests a PCL injury. The posterior drawer test is done in the same fashion as the anterior drawer test, except that the examiner exerts a posterior force. The posterior sag seen in posterior cruciate disruption.The McMurray TestWith the McMurray test, forced flexion and rotation of the knee elicits a clunk along the joint line if there is a meniscus injury. Found in < 10 % of patients with a meniscus injury, joint line pain with the McMurray test is much more common.