Combined instabilities of the knee.

A knee with a combination of instabilities in very difficult to restore to a completely stable condition. The ligamentous structure of the knee is a functional unit. Laxity in any of the planes of the knee motion can produce increased stretching and stress to the structures, which help to provide stability in the other planes. Since it is almost impossible to restore the knee to the pre-injury state, residual laxity in different planes of motion is going to produce increasing stress to the other components, which may have been restored to a greater degree of stability. This emphasizes the importance of a good muscular rehabilitation program and a dynamic component to knee reconstructive procedures to protect against this eventuality. Passive laxity, if present, should not be taken as a sign of failure of the procedure. Often the patient's assessment of his functional capabilities have improved after the reconstructive procedures.