Morphological, Biochemical and Mechanical Features of the Cranial Cruciate and Lateral Collateral Ligaments in Dogs

The cruciate ligament and the collateral ligament play key roles in stabilization of the knee joint. Cases of serious knee joint problems presented at the, the Veteimary Teaching Hospital of Rakuno Gakuen University, Japan mostly involved rupture of the cranial cruciate ligament (CCL). Disorders in structural and biochemical components of the CCL were thought to be the causes of the knee problems. Morphological, biochemical and biomechanical features of the CCL and the lateral collateral ligament (LCL) were therefore analyzed. in the CCL, fibroblasts with ovoid and enlarged nuclei were observed mainly at the periphery ofcollagen bundles. The array ofcollagen fibrils in the LCL was slightly disoriented, but that of the CCL was tight and regular. in the LCL, the major groups of collagen fibnls were those with diameters of 70-80 and 120-130 nm. Most collagen fibrils in the CCL had diameters of 70-80 nm. The mean collagen diameters were 90 nm in the CCL and 105 nm in the LCL. The ratios of the noncollagen area to the area occupied by collagen fibrils were 43% in the CCL and 55% in the LCL. There was no difference between the amounts of HA or between the amounts of DS in two ligaments. However, the amount of CS in the CCL was about 17-times greater than that in the LCL. The expansion of and the resistance to tension exerted onto the CCL were less than those of the LCL. A high concentration of CS and low tensile strength due to small-sized collagen fibrils cause the CCL to rupture easily, especially when overextension of the kneejoint occurs.