Clinical laxity tests and functional stability of the knee: biomechanical concepts.

Biomechanical studies show one or 2 ligaments provide the primary passive restraint for each plane of knee stability with the remaining ligaments having a secondary helping role. Correct interpretation of clinical laxity tests and surgical treatment of instability requires this subdivision. Functional stability of the knee is a primary treatment goal after ligament injury, but is too often short-term, relying on muscle control alone without the fine-tuning action of the ligamentous system. If there is abnormal laxity on the clinical examination, there is an increased risk for joint wear, cartilage deterioration and arthritis on a long-term basis.