Developmental Orthopedic Disease (DOD) in Horses

• Osteochondrosis (OC)
• Osteochondritis Dessicans (OCD)
• Subchondral Bone Cysts (SBC)

  by Robert N. Oglesby DVM

Developmental orthopedic disease (DOD) is a general term for any of the diseases of the musculoskeletal system that occurs during development and growth. This may occur in the fetus or the growing horse and may involve joints or other structures. Osteochondrosis (OC), a type of DOD, is a term for any of a group of diseases of the growth plates or ossification centers in the joints of young horses. Generally there are three forms of OC that are differentiated by their radiographic appearance. To try and make all these letters sensible, here it is in outline form:

• Developmental Orthopedic Disease (DOD)
• Angular deformities these are legs crooked when viewed from the front.
• Flexural deformities are legs that appear contracted or weak when viewed from the side.
• Physeal Dysplasia (Physitis) are legs that have swellings around the joints.
• Ostechondrosis
• Osteochondritis dissecans: defects in the cartilage surface.
• Subchondral bone cysts: defects in the bone underneath the joint.
• intraarticular bone fragments: also called joint mice, they are small pieces of bone or calcified cartilage in the joint space.

Osteochondrosis type diseases are all characterized by degeneration or necrosis of small parts of the epiphysis. This degeneration is sometimes followed by abnormal re-ossification.

All of the diseases under the term OC are defects that create weakness in the joint. When the weakness is such that exercise causes further trauma and damage lameness results. The symptoms of OC can be variable, with some cases causing no problems. Other cases can result in permanent lameness. OC is a lameness of young, growing horses. Usually the onset of lameness is subtle, becoming more obvious as the horse begins working. This article contains possible causes, diagnosis, treatment, prognosis, and has links to forum discussions and other resources on the Internet.