ABSTRACT
Chronic knee instability may occur as a result of undiagnosed acute injury, inadequate treatment or repeated trauma. Stability depends on the cruciate and collateral ligaments (primary stabilizers) and the extrinsic muscles (secondary stabilizers). Some individuals are less dependent on the primary stabilizers than others. Disruption of the complex supporting structures may produce either simple one-plane instability or more complex rotational instability. These can be classified according to the direction of instability noted on stress testing (e.g. anterior draw, pivot shift, etc.).
