The quality of repair tissue produced by defects which exposed the subchondral bone· plate and those which penetrated the subchondral bone plate to expose the subchondral marrow spaces was compared in the equine third carpal bone. Specimens were examined four and six months after surgery. Exposure of the subchondral bone plate resulted in a deep layer of fibrocartilage and a superficial layer of fibrous connective tissue. Exposure of the subchondral marrow spaces resulted in a deep layer of hyaline-like cartilage, an intermediate layer of fibrocartilage and a superficial layer of fibrous connective tissue. Degenerative joint disease occurred in all joints. Results were similar between four- and six-month specimens. Further studies are needed before removal of the subchondral bone plate can be recommended for clinical treatment of full-thickness articular cartilage lesions. / Master of Science