Age-related distribution of elastic fibers in the rabbit knee.

The distribution and histochemical properties of elastic fibers in the knee of newborn, young, adult, and old New Zealand White rabbits were studied. In the growing rabbit, elastic fibers, especially oxytalan fibers, are abundant in the perichondrium and the fibrous layer of the periosteum. They are homogeneously distributed in tendons, ligaments, and menisci, and are absent in the epiphyseal cartilage and growth plate and at the enthesis. In mature rabbits, the articular capsule, the synovial membrane, the peritenon, the periosteum, the perimysium, and the perivascular connective tissue are rich with elastic fibers. They are rarer in the tendon and are absent at the enthesis, in bone and articular cartilage. In the meniscus, the fibers are distributed centripetally. The distribution of elastic fibers is probably related to the different functional role and biomechanical behavior of each tissue. Finally, the type of elastic fiber in the various tissues changes with age; younger animals have more oxytalan fibers than adult animals. A gradual process of maturation and specialization of the network of elastic fibers takes place with age.