Ligamentous Instability

Knee Ligaments

ACL Tear

Anterior Drawer: The patient is positioned supine with the hip flexed to 45 degrees and knee bent to 90 degrees. The examiner grasps the tibia just below the joint line and applies a force to pull the tibia anteriorly.  A positive test is increased anterior translation of involved tiba compared with the uninvolved. Sensitivity: 20%,  Specificity: 88%

Lachman’s: Similar to the anterior drawer excpet the hip is relaxed and knee is flexed to 30 degrees.  Sensitivity: 86% Specificity: 91%

Prone Lachman’s: The patient is prone on a firm examination table.   A small towel roll is placed under the distal end of the thigh and standing on the tested side, the examiner places the hand closest to the foot on the anterior proximal tibia, with the index and long finger on each side of the patellar tendon.  The examiner’s thigh is placed under the patient’s shin to support the knee in 10-30 degrees of flexion.  The heel of the examiners other hand is placed over the posterocentral aspect of the proximal tibia.  The heel of the proximal hand directs an anterior force on the posterior tibia, while the fingers of the distal hand apply slight pressure posteriorly. Sensitivity: 70% Specificity: 97%  + predictive value: 94%  – predictive value: 80%

Pivot Shift: The patient is positioned supine. The examiner applies a slight distraction to the leg just below the knee joint line, with a valgus and internal rotation force is applied to an extended knee.  While maintaining these forces, the knee is flexed past 30 degrees.  Sensitivity: 18-48% Specificity: 97-99%

http://www.youtube.com/watch?v=ZWEGB0ToXZo

Best + predictive value for ruling in a ruptured ACL is a positive pivot shift

The best – predicitve value for ruling out a ruptured ACL is a negative Lachmans

Ostrowski JA. Accuracy of 3 diagnostic tests for anterior cruciate ligament tears. Journal of Athletic Training; 41:120-21.

PCL Tear

1. Posterior Drawer: Patient is supine with their hip flexed to 90 degrees and knee flexed to 90 degrees. The examiner applies a posterior force through the proximal tibia with their thumbs on the plateau. Compare side-to-side for laxity. Sensativity: 91-100% Specificity:80-99%.

2. Posterior Sag Sign: Patient is supine with their hip flexed to 45 degrees and knee flexed to 90 degrees. In this position, the tibia will sag back as compared to the femur if the PCL is torn. Normally the medial tibial plateau should extend 1cm anteriorly beyond the femoral condyle when the knee is at 90 degrees. Sensativity: 79-83%. Specificity: 99-100%.

MCL/LCL Tear

1. Valgus and Varus Stress Tests: Patient is supine with their hip slightly abducted and knee flexed to 30 degrees.  A valgus stress and varus stress is then applied to the medial and lateral compartments of the knee.  A + laxity with valgus stress is indicative of MCL tear and + laxity with a varus stress is indicative of a LCL tear.

Little research has been done on the accuracy of valgus and varus stress tests and the sensativity has varied from 25-86%.

Malanga GA, Andrus S, Nadler SF, McLean J. Physical Examination of the Knee: A Review of the Original Test Description and Scientific Validity of Common Orthopedic Tests. Arch Phys Med Rehabil: 84; 592-603.

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