The importance of the valgus stress test in the diagnosis of posterolateral instability of the knee

Tamir Pritsch, Nehemia Blumberg, Amir Haim, Shmuel Dekel and Ron Arbel

The authors of this study hypothesised that a medial collateral ligament (MCL) tear will also produce a positive dial test and that a valgus stress test would provide differential diagnostic information.  Grade 3 tears to fresh cadaveric knees were simulated and the amount of tibial external rotation (the dial test) was measured for each knee before and after the transection.  The results showed a significant increase in external rotation of the knee in 30° and 90° of flexion. More over, external rotation in 30° was significantly greater than external rotation in 90° of knee flexion. The authors concluded that whenever suspecting a posterolateral complex injury, one has to carefully perform a valgus stress test in 0° and 30°. Although the support of a clinical study is needed in order to make a definite conclusion, the dial test is probably not reliable in the presence of medial instability, and alternative diagnostic measures should be used.

Injury, Volume 37, Issue 10, October 2006, Pages 1011-1014

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