Osteochondrosis (OC) is a developmental disorder where bone formation under the cartilage fails, causing cartilage damage to the affected area. Sometimes, failure to form bone results in a bone cyst (rarer in dogs) and an inflammation of the joint. Osteocondrosis dissecans (OCD) is a state where a detached piece of cartilage is found for instance on a radiograph or by endoscopy. In dogs, osteochondrosis is most commonly found in the shoulder joint. However, the disorder may also affect any other joint, such as the stifle, the tarsus, or the elbow, and also vertebrae. Shoulder osteochondrosis is seen on the caudal humeral head.
A dog may be affected by osteochondrosis in one or more joints, but all changes do not cause the dog to show signs of disease. Osteochondrosis may also occur simultaneously with elbow and hip dysplasia.
A common sign of osteochondrosis is obscure lameness in the age of three to nine months, or at least before the age of one year. The lameness may sometimes be difficult to notice, especially if it is mild or appears on both limbs. Some dogs do not show signs until they have reached adulthood. Dogs with mild shoulder osteochondrosis often show no signs. In radiographs, osteochondrosis is seen as a radiolucent lesion or as a flattened area, under which bone density has usually increased.
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The plan for treatment of shoulder osteochondrosis is made individually for each dog. The treatment plan depends for instance on the size of the dog, severity of signs, and the age of when the signs have first appeared. Conservative treatment including weight control and restriction of exercise may be suitable for a light-structured dog showing no signs or mild signs, whereas especially for heavy-built dogs, surgical treatment is strongly recommended. Older dogs with osteoarthritis are treated conservatively.
Factors that worsen the prognosis include signs of osteochondrosis already at the age of four to five months, severe changes at the time of first signs of disease, and the large size of the dog. Early detection and treatment usually provide a better prognosis and slow down the development of osteoarthritis. In worst case, the dog develops a severe osteoarthritis and/or an inflammation of the bicep tendon.
An osteochondritic change of the bone may heal, remain unchanged, or result in detachment of cartilage (OCD). Osteochondritic changes that have healed or remained unchanged may result in mild osteoarthritic changes, whereas OCD often results in apparent osteoarthritis. A detached piece of cartilage inside the joint and/or joint fluid contact with the bone surface usually causes a sterile inflammation (-> warm, swollen, sore joint). OC and OCD both are different manifestations of the same illness.
Osteochondrosis is a polygenic hereditary disease. Besides from genes, its manifestation is also affected by several other factors (rapid growth, excessive feeding and overweight, physical trauma, circulatory disorder, and hormonal factors). Feeding and possible overweight of a puppy is significant for the development of the clinical disease. Osteochondrosis has been suggested to have a heritability between 0,25 and 0,40. Therefore, its occurrence in a breed can be reduced by systematic, selective breeding. A dog diagnosed with osteochondrosis of any joint must not be used for breeding. It should also be remembered that a dog that shows no clinical signs may pass down genes that cause osteochondrosis to its offspring. Therefore, all relatives of a dog must be taken into consideration when planning a mating.