Knee ligament tests: what do they really mean?

In summary, newer biomechanical concepts clarify human function, the clinical laxity tests, and functional stability of the joint. Biomechanical studies show that one or two 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 require understanding of this differentiation. Knowledge of the interaction between the primary and secondary restraints during the clinical laxity tests allows for more accurate interpretation of the extent of ligament injury. Weak secondary restraints may initially allow little laxity to be demonstrated in the clinical laxity tests. However, the secondary restraints will eventually stretch out and cause a greater laxity. In an acute knee injury, "a little laxity is a lot" and should be considered as serious. In knee injuries, an exact diagnosis of injury is required. This often requires examination under anesthesia and arthroscopy to define the extent of ligament damage. Functional stability of the knee is a primary treatment goal after ligament injury but the stability may be short term if it relies on muscle control alone without the finetuning action of the ligamentous system. Abnormal laxity on clinical examination means increased risk for joint wear, cartilage deterioration, and arthritis on a long-term basis. Close follow-up after ligament injuries, adequate rehabilitation, and correct advice on allowable activities are important treatment concepts after any serious ligament injury.