The etiology for developmental orthopaedic disease is idiopathic, however there are several factors that are suspected etiologies or are predisposing factors. The suspected etiologies for DOD are: ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________
More details on the specific conditions included in developmental orthopaedic disease will be included later in this and other chapters of this text.
Osteochondritis Dissecans (OCD) Osteochondritis dissecans (OCD) is described as a failure in ossification leading to the formation of fissures and flaps in the articular cartilage. It is considered a developmental orthopaedic disease and is seen as a progression of osteochondrosis. The disease process for OCD begins with an idiopathic failure in endochondral ossification which results in the formation of a hypertrophic layer of physeal cartilage. The bone of the epiphysis becomes malformed, most often seen as flattening of the articular surface. The malformation causes increased and stress on the articular cartilage which causes the articular surface to develop fissures or cracks. Damage to the articular cartilage decreases its shock- absorption capacity, putting increased compressive force on the subchondral bone. Over time this pressure causes bone necrosis and the formation of a . If the bone cyst collapses the damaged articular cartilage invaginates into the cyst void and will likely develop into a cartilage flap. Even if the malformation is not severe enough to cause a bone cyst the fissures in the articular cartilage act to increase the friction within the joint and can eventually lead to the development of articular flaps. Articular flaps may tear away from the underlying bone and become joint mice. OCD is seen in young horses less than two years of age. Quarter horses, Thoroughbreds, Standardbreds and warmblood horses are predisposed to developing OCD lesions, and males are reported to have a higher incidence of OCD than females. OCD lesions are commonly seen in the , stifle, shoulder and fetlock joints. Lesions usually present in multiples in a single joint and usually multiple joints are affected simultaneously.
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