The hip joint: the fibrillar collagens associated with development and ageing in the rabbit

The fibrillar collagens associated with the articular cartilages, joint cap sule and ligamentum teres of the rabbit hip joint were characterised from t he 17 d fetus to the 2-y-old adult by immunohistochemical methods. Initiall y the putative articular cartilage contains types I, III and V collagens, b ut when cavitation is complete in the 25 d fetus, type II collagen appears. In the 17 d fetus, the cells of the chondrogenous layers express type I co llagen mRNA, but not that of type II collagen. Types III and V collagens ar e present throughout life, particularly pericellularly. Type I collagen is lost. In all respects, the articular cartilage of the hip joint is similar to that of the knee. The joint capsule contains types I, III and V collagen s. In the fetus the ligamentum teres contains types I and V collagens and t he cells express type I collagen mRNA, type III collagen is confined mainly to its surface and insertions. After birth, the same distribution remains, but there is more type III collagen in the ligament, proper. The attachmen t to the cartilage of the head of the femur is marked only by fibres of typ e I collagen traversing the cartilage; the attachment cannot be distinguish ed in preparations localising types III and V collagens. The attachment to the bone at the lip of the acetabulum is via fibres of types I and V collag ens and little type III is present. The ligament is covered by a sheath of types III and V collagens. Type II collagen was not located in any part of the ligamentum teres. The distribution of collagens in the ligamentum teres is similar to that in the collateral ligaments of the knee. Its insertions are unusual because no fibrocartilage was detected.