Structure and Function of Matrix Components in the Cruciate Ligaments

Abstract

In the present study, the matrix components of 100 cruciate ligaments were analyzed by conventional electron microscopy, immunohistology, morphometry, and immunoelectron microscopy. The anterior (ACL) and the posterior (PCL) cruciate ligaments contained collagen types III, IV, and VI. Several structural glycoproteins, like fibronectin, laminin, entactin, tenascin, and undulin were detected using monoclonal antibodies. Whereas laminin and entactin were higher concentrated in the PCL, type VI collagen was more frequently found in the ACL. The ACL had a critical nourishment in its distal and middle thirds. In all ligament parts the PCL revealed a better vascular supply with strong correlation to type IV collagen expression. The normal matrix of the cruciate ligaments represented a complicated regulatory network of proteins, glycoproteins, elastic systems, and glycosaminoglycans with multiple functional interactions.

Anatomy of the anterior cruciate ligament

“…Studies suggest that the ACL has different histological characteristics from the MCL or tendon, and is more cartilage‐like in nature. As an example, a zone of fibrocartilage is noted in the distal third of the ligament adjacent to the roof of the intercondylar notch (see below) [38, 39]. The distal part, which is the most solid, is rich in chondroblasts and ovoid fibroblasts (Fig.…”

“…Type III collagen has a nearly ubiquitous distribution in the ACL, but reveals maximal concentrations near the attachment zones. It is important for the pliability of the ligament, and may also serve to anchor vessels to the adjacent matrix as it bridges collagens and basement membranes [39]. Most of the newly synthesized collagen in the early phase of healing is type III [56].…”

“…Type IV collagen is found in all vascular basement membranes, mainly in the proximal and distal parts of the ACL and less in the middle third which is less vascularized [39].…”

“…It is present in higher amounts in the proximal and distal thirds rather than the middle part of the ACL. This distribution is due to significantly higher strains in the attachment regions in comparison with the mid‐region [39].…”

Age-related changes in human PCLs: a light and electron microscopic study

“…In the literature there are many studies of the anterior cruciate ligament (ACL) [6,9,11,12] but only few dealing with the PCL [1,5]. Neurath and Stofft [8] examined the matrix components of 100 cruciate ligaments and found collagen types III, IV, and VI in ACLs and PCLs. Neurath et al [10] compared the collagenous fiber systems of the ACL and PCL, and in the latter they observed more type IV collagen, many intrinsic vessels, thicker fibrils, and paral-lel fiber arrangement.…”