Cranial cruciate ligament structure in relation to the tibial plateau slope and intercondylar notch width in dogs.

Cranial cruciate ligament (CCL) rupture is one of the most common orthopedic conditions in dogs. The pathogenesis of CCL rupture is not fully described and remains to be elucidated fully. Several hypotheses have been proposed to explain the etiology of these changes. The objective of this study was to investigate structural changes in the CCL in relation to the tibial plateau angle (TPA) and the intercondylar notch (ICN) width in dogs. Fifty-five skeletally mature dogs were included in this study. ICN width and TPA measurements were obtained from intact CCL stifles. Samples of the CCL, caudal cruciate ligament (CaCL), and femoral head ligament (FHL) were harvested and stained for routine histological and immunohistochemical analysis. Microscopic changes in the ligaments were observed and were found to correlate with the TPA and ICN width values. The degree of structural changes within the CCL was observed to correlate with an increasing TPA and a narrowing ICN width. Changes in the CCL are likely to be caused by excessive forces acting through the ligament in stifles with a high TPA. Chondroid metaplasia of the CCL is an adaptation to abnormal mechanics within the stifle joint caused by altered bone morphology.