THE ROLE OF THE CRUCIATE AND POSTEROLATERAL LIGAMENTS IN STABILITY OFTHE KNEE - A BIOMECHANICAL STUDY

The role of the posterolateral and cruciate ligaments in restraining k nee motion was studied in 11 human cadaveric knees. The posterolateral ligaments sectioned included the lateral collateral and arcuate ligam ents, the popliteofibular ligament, and the popliteal tendon attachmen t to the tibia. Combined sectioning of the anterior cruciate and poste rolateral ligaments resulted in maximal increases in primary anterior and posterior translations at 30 degrees of knee flexion. Primary varu s, primary internal, and coupled external rotation also increased and were maximal at 30 degrees of knee flexion, Combined sectioning of the posterior cruciate and posterolateral ligaments resulted in increased primary posterior translation, primary varus and external rotation, a nd coupled external rotation at all angles of knee flexion. Examinatio n of the knee at 30 degrees and 90 degrees of knee flexion can discrim inate between combined posterior cruciate ligament and posterolateral injury and isolated posterolateral injury. The standard external rotat ion test performed at 30 degrees of knee flexion may not be routinely reliable for detecting combined anterior cruciate and posterolateral l igament injury. However, measurements of primary anterior-posterior tr anslation, primary varus rotation, and coupled external rotation may b e used to detect combined anterior cruciate and posterolateral ligamen t injury,