The cranial horn of the medial meniscus is the most common site of soft tissue injury in the equine stifle. These injuries occur as tears that are commonly associated with secondary osteoarthritis and a poor prognosis for return to athletic performance. Experimental research evaluating equine meniscal tears is lacking. One goal of this thesis was to document the translocation and deformation of the equine menisci throughout the complete range of motion of the femorotibial joint in order to evaluate for potential mechanical factors in the pathogenesis of cranial horn injury. An additional goal was to assess the tensile forces and microanatomic structure of the cranial horn of the medial meniscus to further evaluate the pathogenesis of these lesions. In the third study, the pathophysiology of these lesions was evaluated by determining the effect of grade III cranial horn tears of the medial meniscus on the magnitude and distribution of contact forces on the medial tibial condyle. Results indicate that full extension of the femorotibial joint leads to cranial displacement and axial compression of the cranial horn of the medial meniscus, and an ensuing increase in tensile forces in the adjacent cranial horn attachment. Therefore, injury of the cranial horn of the medial meniscus may occur during hyperextension of the stifle joint. Histologic findings indicate that the characteristic pattern of these tears may be partly explained by the ultrastructure of the cranial meniscotibial ligament. Grade III meniscal tears resulted in alterations in the magnitude and distribution of contact forces on the medial tibial condyle that may contribute to the development of secondary osteoarthritis.
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