Osteochondrosis (OC) is being increasingly recognized as a leading cause of lameness in many large-breed dogs such as the Rottweiler, Labrador retriever, Bernese mountain dog and Newfoundland. OC is a developmental disease which means affected pets are born with a defect in normal joint (cartilage) development. This defect typically causes lameness at an early age.
This abnormal development results in various clinical syndromes. All of the elbow diseases that occur in young dogs secondary to OC can be lumped together under the term "elbow dysplasia." Fragmented coronoid process (FCP) of the elbow joint. Currently the most important of the diseases that fit under the umbrella of OC, FCP results from either an abnormal cartilage development of the coronoid process of the ulna or an abnormal development in the length of the radius and ulna bones between the elbow and wrist. A small piece of the coronoid process fragments (hence the name fragmented coronoid process) inside the elbow joint sometime between 4 to 6 months of age. This very small fragment elicits a secondary arthritis at an early age (five to ten months).
This is similar to the irritation you experience in your foot when you have a rock in your shoe. The clinical signs are somewhat subtle and non-specific; you may notice lameness in your pet or simply that your pet seems reluctant to exercise. This condition is frequently bilateral, although one side is often worse, and your pet may not show any clinical signs until years later when the secondary degenerative joint disease predominates.
Osteochondritis dissecans (OCD). This joint condition is related to OC. OCD can occur in the shoulder, stifle (knee), hock (joint below the knee) and elbow. OCD of the shoulder was once the most commonly recognized form of OC; however, FCP is now more commonly diagnosed. OCD of the shoulder occurs when there is abnormal ossification or development of the joint cartilage of the upper portion of the humerus. A layer of thicker cartilage results from the osteochondrosis. This thicker cartilage can crack, cause a fissure and dissect (hence the name dissecans) a cartilage flap. This causes secondary joint inflammation and lameness. Like FCP, OCD affects young, large-breed dogs. This condition also frequently affects both front legs.
Ununited anconeal process (UAP) is generally thought to fit under the umbrella of OC. In dogs with this disease the anconeal process of the ulna separates from the host bone and causes a large, free piece of cartilage and bone in the elbow joint. This causes severe secondary degenerative arthritis. Although originally reported in young German shepherd dogs, this disease has been reported in most large breeds. UAP has also been reported in large chondrodystrophied (dwarf-like with short, curved legs) breeds, like the basset hound.