Codominance of the individual posterior cruciate ligament bundles - An analysis of bundle lengths and orientation

Background: It is unclear how each bundle of the posterior cruciate ligament contributes to posterior knee stability. Hypothesis: Changes in bundle orientation and length occur such that neither bundle dominates in restraining posterior tibial motion throughout knee flexion and extension. Study Design: Controlled laboratory study. Methods: Six fresh-frozen cadaveric knees were studied in a joint-testing rig with individual quadriceps and hamstring muscle loading. Kinematic data for the tibia and femur were obtained at knee flexion angles from 0degrees to 120degrees. The joint was then disarticulated, and the insertions of the two bundles on the tibia and femur were digitized. Results: Length of the anterolateral bundle increased with increasing knee flexion angle from 10degrees to 120degrees. Length of the posteromedial bundle decreased with increasing knee flexion angle from 0degrees to 45degrees and increased slightly from 60degrees to 120degrees. Length of the anteromedial bundle was significantly less than that of the posteromedial at 0degrees, 10degrees, and 20degrees of knee flexion. The anterolateral bundle was significantly more horizontal at flexion angles of 0degrees, 10degrees, 20degrees, 30degrees, and 45degrees (P < 0.05). The posteromedial bundle was more horizontal at 120degrees. Conclusions: Changes in orientation take place such that neither bundle dominates in restraining posterior tibial motion throughout knee flexion and extension. Clinical Relevance: Double-bundle reconstructions achieve more physiologic knee function. (C) 2003 American Orthopaedic Society for Sports Medicine.