Overview of Osteochondritis Dessicans
Osteochondritis dessicans (OCD) is a hereditary disease that occurs early in the development of some dogs, and less often in horses and cats. The condition is characterized by cracks and flaps in articular cartilage, which cause inflammation, joint instability, pain, lameness, and degenerative joint disease.
Endochondral ossification is the process by which cartilage on the ends of long bones (e.g., humerus, femur) ossifies, or changes to bone. If cartilage does not calcify properly, it thickens and prevents synovial fluid from reaching cartilage cells beneath it. Without synovial fluid, the cells degenerate and die, causing cracks in the cartilage. The cracked cartilage is weak and does not adequately attach to the bone, and the bone does not reach its full length. During movement, the cracked cartilage causes pits and abrasions to form on the bone.
Cartilage cracks can deepen and one or more small pieces of cartilage may loosen, resulting in flaps that may calcify. Cartilage flaps rub against underlying tissue, causing pain, lameness, and eventually degenerative joint disease.
Sometimes flaps of cartilage detach. In some cases, they are reabsorbed and in others, they float inside the joint capsule, grow, and eventually interfere with movement. "Joint mice" can become wedged between the bones of the joint, eroding cartilage and causing severe pain.
The body attempts to compensate for the damaged cartilage by forming scar tissue or by adding bone to the affected area (i.e., remodeling), increasing instability and irritation.
Incidence and Prevalence of Osteochondritis Dessicans
More than 10 percent of dogs develop OCD in one or more joints. The condition is more prevalent in large and giant breeds such as:
- Great Dane
- Labrador retriever
- Bernese mountain dog
- English setter
- Old English sheepdog
- Golden retriever
- German shepherd
Other large breeds (e.g., Doberman pinscher, collie, Siberian husky) have a low incidence of OCD.
OCD of the shoulder occurs twice as often in male dogs than in female dogs and OCD of the hock occurs more often in females. The disease occurs less frequently in horses and cats than in dogs.