Histological evaluation and comparison of the anteromedial and posterolateral bundle of the human anterior cruciate ligament of the osteoarthritic knee joint.

A human anterior cruciate ligament (ACL) is composed of an anteromedial (AM) and posterolateral (PL) bundle which have different biomechanical functions. ACL degeneration and ACL deficiency often occur in patients with osteoarthritis (OA); however, histological evaluation of each bundle of the ACL in the OA knee has not been reported. Our objective was to compare the degenerative changes of the AM and PL bundle in the OA knee based on histological appearance. A histological evaluation of the AM and PL bundle from 49 varus OA knees was performed. Fifty-three percent of the AM bundle and 78% of the PL bundle showed severe histological degenerative changes. The degenerative changes were statistically more severe in the PL bundles than the AM bundles (p<0.05). Since the cross sectional area of the AM bundle is larger than that of the PL bundle and the pattern of length change of the PL bundle is greater than that of the AM bundle, it would logically follow that the PL bundle would show more severe degenerative changes than the AM bundle. This study identified the histological appearance of the bundles of the ACL of the OA knee and may help to elucidate the process of ACL degeneration in the OA knee.