Based on the clinical and operative findings in sixty-eight knees with
acute tears of the medial compartment and cruciate ligaments, a
standardized terminology and classification of knee ligament instability is
presented. With an intact posterior cruciate ligament, anteromedial,
anterolateral, or posterolateral rotatory instability may occur, but not
true posteromedial rotatory instability. With the posterior cruciate
ligament ruptured, straight anterior, posterior, medial, or lateral
instability may be found.