Posterolateral aspect and stability of the knee joint. II. Posterolateral instability and effect of isolated and combined posterolateral reconstruction on knee stability: a biomechanical study.

This study evaluated the correlation between the number of transected posterolateral structures (PLS) and the grade of posterolateral rotational instability, determined the effect of the popliteus muscle-tendon unit on the tibial rotation, and examined the effect of an isolated posterior cruciate ligament (PCL) and combined PCL-PLS reconstruction on knee stability. Sectioning the popliteofibular and lateral collateral ligaments both caused an increase in tibial external rotation. Cutting the PT resulted in a statistically highly significant excessive external rotation and externally shifted neutral position of the tibia over the full range of motion. Tensioning the popliteus muscle-tendon unit led to a statistically highly significant internally shifted neutral tibial rotation and a decreased internal and an increased external rotation without affecting the total rotational arcs. The isolated PCL reconstruction did not affect the external rotation, whereas the combined PCL-PLS reconstruction reset the knee to nearly physiological laxity patterns.