Why is the elbow an important joint?
The dog carries about 65% of his weight on his front end. Not only do the front legs bear most of the concussion when a jumping dog lands, they also provide a good deal of the propulsion necessary to launch him into the air. The shoulder and elbow joints absorb most of the impact during movement. Those "turn on a dime" movements our Belgians are so fond of can really put some stress on the joints of the forelimb!
How does the elbow work?
The elbow joint joins the humerus, the upper arm bone, to the radius and ulna, the bones that lie between the carpus (wrist) and the elbow. This part of the dog is very similar to the set up of your upper arm, elbow, forearm and wrist. The point of your elbow is the top of your ulna. If you could look at the elbow from the front, you’d see the end of the humerus has a hole in it, on either side of the hole are wheel like structures called condyles. These condyles fit into little depressions on top of the radius. Now, looking from the side, you can see that the head of the ulna is shaped like a C. The top part of the C is a projection of bone called the anconeal process. This projection fits into the hole between the condyles of the humerus. The bottom part of the C is formed by another projection of bone called the coronoid process, and the head of the radius.
All of these bone ends are covered with a smooth form of cartilage that lets the bones glide easily on each other, so the dog can flex and extend his elbow like a well made hinge.
What is elbow dysplasia?
This term is used to describe several developmental abnormalities of the elbow joint, including fragmented coronoid process of the ulna, OCD of the humeral condyle, un-united anconeal process, and joint incongruity (the bones don’t fit together properly).
What in the world is OCD?
Osteochondritis Dissecans is a disease that occurs when bone is growing. In young dogs, the bones have growth plates made of cartilage in areas where growth will occur. Bone grows by changing its cartilage growth centers into bone, layer by layer. If this process is disturbed, the cartilage may not calcify properly, it just grows thicker. This thick spot of cartilage doesn’t receive a proper blood supply so it dies and cracks form. This leaves a defect in the cartilage covering the end of the bone. If the growth plate for the anconeal process or the coronoid process doesn’t calcify properly, the little bony projections won’t attach to the ulna. A problem in any of these areas means that the elbow joint won’t fit together properly and will be unstable, this can cause lameness and eventually arthritis.
Is elbow dysplasia inherited?
Elbow dysplasia, like hip dysplasia, is a multifactorial disease. Both genetics and environment may contribute to the development of the disease. Several studies have shown elbow dysplasia to be highly heritable. Elbow dysplasia is considered to be more highly heritable than hip dysplasia.
How can I tell if my dog has elbow dysplasia?
Cases may become apparent during puppyhood, often around 4 or 5 months of age. Affected dogs may be lame all the time, or the lameness may come and go. The dog may be stiff for the first few minutes after rising. Both legs may be affected making it hard to tell the dog is lame. He may stand with his elbows close to his chest and be painful when the elbow is extended. At 5 months, x-rays will show if the anconeal process is not united. If the problem is one of the other components of elbow dysplasia, it may not show up on an x-ray until the dog is over a year old.
Dogs that show lameness will likely develop degenerative joint disease over time. For every lame dog, there are many more with subclinical disease. These dogs may become lame at a later time, or if bred, their offspring will have a higher incidence of elbow dysplasia than the offspring of dogs with normal elbows.
How can I help prevent the spread of elbow dysplasia?
Dogs over 24 months old can be screened by taking x-rays of the elbow. These films can be screened by the Orthopedic Foundation for Animals (OFA) just as hip films are screened. Dogs with normal elbows will be assigned a number.
When an abnormality is found they are graded:
Grade I-minimal bone change on the anconeal process
Grade II-additional bone changes or bone spurs
Grade III-well developed degenerative joint disease.
The latest available figures from OFA (Dec. 98) put the incidence of elbow dysplasia at 4.3 percent of a total of 490 examinations. These figures tend to be artificially lowered as films with obvious lesions are often not submitted for screening. The incidence of elbow dysplasia appears to be fairly low in the Belgian Tervuren at this time. With a concerted effort on the part of breeders it will hopefully stay that way!!
Libbye Miller, DVM
Reprinted with permission fromThe Belgian Sheepdog