Topographical histology of the posterolateral corner of the knee, with special reference to laminar configurations around the popliteus tendon: a study of elderly Japanese and late-stage fetuses

Abstract

We investigated the histology of laminar configurations at the posterolateral corners of 40 knees (18 late-stage fetuses, 22 elderly persons). In the fetuses, the deeply located popliteal fascia and the superficially located inferior geniculate vascular sheath were evident in a space between the popliteus tendon (PT) and the biceps femoris and gastrocnemius. Along, and deep to, the popliteal fascia, the popliteus muscle parenchyma developed into both the PT and another dense connective tissue mass. The PT attached to the fibula (i.e., the fetal popliteofibular ligament) and to the base of the lateral meniscus (i.e., the fetal popliteomeniscal fasciculus). This laminar configuration was essentially maintained in the elderly. The fetal dense connective tissue of the popliteus origin seemed to correspond to the adult arcuate ligament. However, because a connective tissue complex (including the PT and the arcuate and popliteofibular ligaments) was often well developed, the complex involved the inferior geniculate vascular sheath and popliteal fascia. A spectrum of variations was found in how thickly the complex developed. Thus, clear separation of the PT from the surrounding tissues often became difficult. Notably, the connective tissue complex could be peeled in different manners, depending on the site and the individual. Therefore, macroscopic variation in the posterolateral corner, including the apparent absence of some ligaments, seemed to be related to the thickness and number of layers developed by the connective tissue complex, possibly due to an adaptation to the individual’s mechanical environment during growth and aging.