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.