Association of mineralisations in the stifle joint of domestic cats with degenerative joint disease and cranial cruciate ligament pathology

The aim of the study was to evaluate the prevalence, size, location and appearance of mineralisations in feline stifle joints, and to evaluate their relationship with osteoarthritis and cranial cruciate ligament (CrCL) status. Presence or absence, and size of mineralisations were determined from lateral stifle radiographs of 25 cats with CrCL rupture, and 44 cat cadavers without CrCL rupture. Mineralisations were classified as small, medium or large. Prevalence was compared between the clinically affected cats and the cadavers; the cadaver group was subdivided into an age-matched and an older group. Ten stifles with varying sizes of mineralisations were prepared as whole-knee specimens for histopathology. Location and appearance of the mineralisations, and degenerative changes in the cruciate ligaments, menisci, articular cartilage and joint capsule are described. Prevalence of articular mineralisations was 0.76 in stifles of cats with CrCL rupture (mean ± SD age 8.6 ± 4.5 years), 0.64 in stifles of age-matched cat cadavers and 0.74 in older cat cadavers (mean ± SD age 17.0 ± 2.4 years). Cats with CrCL rupture had a higher percentage of medium and large mineralisations than cats without CrCL rupture. Microscopically, small mineralisations were calcifications usually located in the cranial horn of the medial meniscus. Larger mineralisations were found to be ossifications, commonly located in the joint capsule and fat pad. Cats with larger mineralisations showed more signs of osteoarthritis, including degenerative changes in the CrCL. Mineralisations in feline stifle joints were found to differ in size, appearance and location. Small mineralisations were usually confined to the medial meniscus, as described previously; larger mineralisations tended to be located in the tissues cranial to the menisci and seemed to be associated with osteoarthritis and CrCL pathology. Large mineralisations in feline stifles are ossifications in periarticular tissue and are associated with degenerative joint disease.