Cranial cruciate ligament (CCL) rupture is one of the most common orthopaedic conditions in dogs. The pathogenesis of CCL rupture is not fully understood and remains to be elucidated. Several hypotheses have been proposed to explain the aetiology of these changes. The objective of this study was to investigate structural changes in the cranial cruciate ligament (CCL) in relation to the tibial plateau angle (TPA) and 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 values of the TPA and ICN width. The degree of structural changes within the CCL was observed to correlate with an increasing TPA and a narrow 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.
KEYWORDS: CCL; ICN; TPA; arthritis; stifle