Anatomy of the collateral ligaments of the feline elbow joint: functional implications.

Cats show a higher capability to supinate their forearms than dogs. This suggests a special arrangement of the collateral ligaments of the feline elbow joint. Therefore, the course of the ligaments was examined in 13 adult cats. The size of the ligaments was measured, and effects of passive joint movements were studied. Ligaments of five additional cats were examined histologically. The lateral collateral ligament (LCL) had a superficial and deep part, both originating from the humerus. The free humeral portion of the LCL was short and contained fibrous cartilage. Fibre bundles of the deep part inserted into the annular ligament, while the remaining deep fibres and the superficial part inserted with a long antebrachial portion on the radius. The medial collateral ligament (MCL) originated from the humeral epicondyle and divided into cranial and caudal parts. The caudal part inserted medioproximally on the ulna, while the cranial part attached primarily with a long thin part to the caudal aspect of the radius. During supination, the MCL loosened thus allowing medial widening of the joint space, up to 2 mm. A specific feature of the feline elbow is the long thin part of the MCL. Its course through a special furrow distal to the medial coronoid causes the tightening of the feline MCL during pronation. Apart from that, the feline collateral ligaments combine the features of both human and canine cubital anatomy. This explains the range of supination in cats, which is intermediate between humans and dogs.