[Radiologically detectable changes in the radial annular ligament and the supinator muscle of the domestic cat (Felis...

Elbow joints of a random sample of 59 cats were investigated by means of X-rays and dissection as well as histologically and by making cuts through synthetic resin-embedded joints. Bone-dense shadow craniolateral to the elbow joint was observed in X-ray images of 23 limbs (about 20%). Furthermore 8 of these 23 elbow joints (about 7%) showed signs of arthrotic alteration. Histologic examination revealed one or more centers of metaplasia of varying status of development of the annular ligament of the radius. Alterations varied from chondroid metaplasia to mineralisation and ossification. They turned out to be located in the area where the annular ligament of the radius crosses the tendon of origin of the supinator muscle and are considered to be a reaction of tough connective tissue to mechanical stress. Compressive forces seem to be less responsible than tensile stress. As soon as bone-dense shadow is observed in X-ray images, alterations have grown so far as the annular ligament of the radius as well as the tendon of origin of the supinator muscle are affected.