Measurement of Rotational Laxity of the Knee: In Vitro Comparison of Accuracy Between the Tibia, Overlying Skin, and Foot

Background: Posterolateral corner (PLC) injuries are difficult to diagnose and cause significant morbidity. The ideal method for the dial test and its accuracy remain unclear.Purpose: This study compares the accuracy of measuring tibial external rotation at the skeletal level to measuring the patella-tubercle angle (PTA) and the thigh-foot angle (TFA) in the supine position to assess the most accurate method to measure rotation during the dial test.Study Design: Controlled laboratory study.Methods: Measurements were compared simultaneously using rotational goniometers at a cutaneous splint over the tibia, at a foot splint, and directly from the tibial skeleton. Six lower limbs were used. The femur was held rigidly and the knee tested at 90° and 30° of flexion. External rotation torque up to 8 N·m was applied through the foot splint, and the rotations were measured by 2 testers.Results: Measurements at the tibial splint and directly on the tibia showed significant correlation at both knee flexion angles. T...