Anterior cruciate ligament: functional anatomy of its bundles in rotatory instabilities.

The functional anatomy of tha anterior cruciate ligament was studied in 18 freshly amputated specimens. The cruciates were observed in the extremes of flexion and extension, and in midposition in simulated weight-bearing and nonweight-bearing conditions. Five femoral shafts were split longitudinally so that the femoral and tibial attachments of the ligament could be inspected. The findings indicated that (1) the anterior cruciate ligament is a secondary static stabilizer against rotatory instabilities of the knee; (2) the anteromedial bundle contributes to anterolateral stability; (3) the intermediate bundle adds to straight and anteromedial stability; and (4) the posterolateral bundle assists in posterolateral stability. Specific bundles and functions of bundles must be considered in reconstruction, substitution, or replacement of the anterior cruciate ligament.