CHANGES IN THE DISTRIBUTION OF FIBRILLAR COLLAGENS IN THE COLLATERAL AND CRUCIATE LIGAMENTS OF THE RABBIT KNEE-JOINT DURING FETAL AND POSTNATAL-DEVELOPMENT

The collateral Ligaments can be clearly distinguished in the 25-day fe tal rabbit knee joint. Types I and V collagens are present in the extr acellular matrix between the cells of the lateral and medial collatera l ligaments and this distribution persists until the rabbit is skeleta lly mature. From 8 months onwards type III collagen is also present, p articularly around the cells. Type I collagen mRNA is expressed by the cells from the 25-day fetal to 8-month-old adult Ligament, The ligame nt sheath is composed of types III and V collagens. The cruciate Ligam ents are present between the femur and tibia in the 20-day fetus. The matrix is composed of types I and V collagens from the 25-day fetus un til at 12- to 14-weeks postnatal, type Ill collagen appears in the per icellular regions together with type V. At 8 months and 2 years, the a mount of type III collagen has increased. All the cells express the mR NA for type I collagen at 12- to 14-weeks, but only isolated cells exp ress this mRNA at 8 months. Thus, both the collateral and cruciate lig aments undergo changes in their complement of collagens during postnat al development and ageing. The implications of these complex interacti ons of different types of collagen are discussed in relation to healin g and the surgical replacement of tom ligaments by tendons.