Classification of knee ligament instabilities. Part II. The lateral compartment.

Lateral instability of the knee is less frequent but more disabling than medial instability of a comparable amount. At the same time the diagnostic tests for lateral instability are more subtle and more frequently misinterpreted. Posterolateral rotatory subluxation is demonstrated by an apparently positive posterior drawer test with the tibia in neutral rotation or by the external rotation-recurvatum test with the knee in extension. Anterolateral rotatory subluxation is present when the anterior drawer test with the tibia in neutral rotation demonstrates that the lateral tibial condyle appears to become more prominent or that both condyles appear to become equally prominent.