Elbow dysplasia is a common cause of front-leg lameness in large-breed dogs. Breeds predisposed to elbow dysplasia include the Golden Retriever, Labrador Retriever, English Setter, English Springer Spaniel, Rottweiler, German Shepherd, Bernese Mountain Dog, Chow Chow, Chinese Shar-Pei, Newfoundland, and others.
The elbow joint is composed of the humerus, which articulates with the radius and ulna, and those two bones. The anconeal processunites with the ulna at about 6 months of age. It forms a curved depression in the ulna. The coronoid process forms part of the lower curved bone of the ulna.
Dogs with elbow dysplasia have one or more of the following inherited developmental defects, which may occur singly or in combination: ununited anconeal process, fragmented medial coronoid process, osteochondritis dissecans of the medial condyle of the head of the humerus, and incongruity of growth rate between the radius and ulna resulting in curvature of the radius. The first three defects are related to osteochondrosis. The fourth is related to an enlargement of the epiphyseal growth plate at the head of the radius.
Signs of elbow dysplasia usually appear in puppies at 4 to 10 months of age, but some dogs may not show signs until adulthood, when degenerative joint disease starts. The signs consist of varying degrees of front-leg lameness that worsens with exercise. Characteristically, the elbow is held outward from the chest and may appear swollen.
The diagnosis is made using detailed X-rays of the elbow joint, taken in extreme flexion. Radiologists are particularly interested in the appearance of the anconeal process of the ulna. In a dog with elbow dysplasia, the anconeal process has a rough, irregular appearance due to arthritic changes. Another sign of dysplasia is widening of the joint space associated with a loose, unstable joint. X-rays may be difficult to interpret before a pup is 7 months of age. A CTscan may be required to demonstrate a fragmented coronoid process.
The OFA evaluates X-rays and maintains registries for dogs with elbow dysplasia. Dogs must be 24 months of age or older to be certified by OFA, although it accepts preliminary X-rays on growing pups for interpretation only.
Treatment: Medical treatment is similar to that described for Hip Dysplasia, page 392. Surgery is the treatment of choice for most dogs. Several factors, including the age of the dog and the number and severity of the defects, govern the choice of surgical procedure. The more defects in the elbow, the greater the likelihood that the dog will develop degenerative arthritis-with or without surgery.
Bone lengthening is a continuous process in which rapidly growing cartilage at the ends of bones becomes calcified and is gradually incorporated into the bone. Osteochondrosis is a disease caused by a defect in the calcification process of this growing cartilage. In a dog with osteochondrosis, the cartilage is calcified in an irregular instead of a uniform fashion. This creates areas of uncalcified, defective cartilage over the ends of the bones. With stress on the joint, the defective cartilage breaks into loose fragments called joint mice. This process, which is accompanied by joint pain and swelling, is called osteochondritis dissecans.
Osteochondrosis most often involves the head of the humerus in the shoulder joint. It also occurs in the elbow, where it is responsible for many of the defects of elbow dysplasia. Osteochondrosis occurs less commonly in the stifle and hock joints. In the stifle, osteochondrosis involves the femur at its articulation with the tibia. Symptoms of intermittent lameness may look like luxating patella. In the hock, osteochondrosis involves the articulation between the tibia and the talus (the first bone of the hock).
Osteochondrosis is a common disease of rapidly growing large-breed puppies. The first signs show up at between 4 and 8 months of age. The symptoms may resemble those of panosteitis (see this page), another disease that causes lameness in growing puppies. The typical presentation is gradual lameness that seems to stem from the shoulder, elbow, stifle, or hock in a young dog of one of the large breeds. Lameness often gets worse with exercise. Symptoms may appear following a traumatic episode such as jumping down stairs. Pain is present on flexing and extending the joint. X-rays may show fragmentation of joint cartilage or a loose piece of cartilage in the joint. The diagnosis may not be made definitively until the dog is 18 months of age.
Treatment: Medical treatment involves restricting activity and prescribing analgesics and chondroprotectants,as described for the treatment of degenerative joint disease. Preparations that contain polysulfated glycosaminoglycan (such as Adequan) may be of benefit in limiting further cartilage degeneration and relieving pain and inflammation.
In most cases surgery will be required to scrape away defective cartilage and remove any joint mice. The best results are obtained in the shoulder and elbow joints. The results are less favorable for the hock, which is a small joint, and for the stifle, which is a more complex joint. In the hock and stifle, degenerative joint disease is likely to occur over time.
This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.