Knee ligament instability--a rational anatomical classification.

In the management of a number of acute and chronic knee ligament injuries it was noted that the patterns of displacement could be explained on a translational basis in one of two planes. The displacement could be predicted by the anatomical structures that were torn. Rotation, while present in some cases, was not the major pattern of instability. It is therefore logical to classify knee ligament injuries on an anatomical basis. The injury or combination of injuries produces a predictable pattern of instability. Anatomical classification based on patterns of instability is less confusing than some methods of classification currently in use and may aid in clinical management.