Evaluation of Posterolateral Rotatory Knee Instability Using the Dial Test According to Tibial Positioning

Purpose This study examined the effect of the anteroposterior (AP) direction force on the tibial external rotation of a posterior cruciate ligament (PCL)/posterolateral corner (PLC)–deficient knee in a clinical setting. Methods Between December 2006 and December 2007, 21 patients with a PCL-PLC injury were assessed using a dial test. The thigh-foot angle (TFA) and patella-tubercle angle (PTA) were measured with an external rotation stress applied to the tibia at both 30° and 90° of knee flexion in 2 different positions (reduced and posterior subluxed). The test was performed with the patient in the supine position and with an AP force applied to the tibia by an assistant. To reduce intra- and interobserver bias, the measurements were taken twice by 2 orthopaedic surgeons for all patients. Results In the subluxed position, the mean side-to-side differences in the TFA at 30° and 90° knee flexion were 12.6° ± 2.0° and 12.3° ± 1.4°, respectively. In the reduced position, the mean side-to-side differences in the TFA at 30° and 90° knee flexion were 18.4° ± 1.4° and 18.5° ± 1.5°, respectively. In the subluxed position, the mean side-to-side differences in the PTA at 30° and 90° knee flexion were 9.1° ± 0.8° and 9.0° ± 0.7°, respectively. In the reduced position, the mean side-to-side differences in the PTA at 30° and 90° knee flexion were 13.3° ± 0.6° and 13.2° ± 0.6°, respectively. Conclusions The reduction of a posteriorly subluxed knee increased the tibial external rotation (TFA and PTA) during the dial test of combined PCL-PLC injuries in a clinical setting. The accuracy of the dial test may help present surgeons from missing a combined PLC injury that should be corrected in a PCL deficient knee. Level of Evidence Level I, testing of previously developed diagnostic criteria in series of consecutive patients.