Canine Hip Dysplasia - Research Article
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| Definition | Risk Factors | Effects |
| Symptoms | Diagnosis | Prevention |
What is Hip Dysplasia?
Canine Hip Dysplasia (CHD) is an abnormal function of the hip joint. Though the veterinary community knows a lot about CHD, many elements of the disorder remain a mystery. This article attempts to distinguish fact, theory, hypothesis, and the unknown.
Understanding the Hip Joint
To understand what hip dysplasia really is, one must start with an understanding of the hip joint. The hip joint forms the attachment of the hind leg to the body by way of a “ball and socket.” The ball portion is the head of the femur (the long bone extending from the hip to the knee), while the socket (known as the acetabulum) is located on the pelvis. In a normal joint, the ball rotates freely, and snugly, within the socket. To facilitate movement, the bones are shaped to match each other perfectly, with the socket surrounding the ball. The two bones are held together by a ligament, which strengthens the joint, and attaches the femoral head directly to the acetabulum. The joint capsule, which is a very strong band of connective tissue, encircles the two bones and adds further stability. The area where the bones actually touch each other, the articular surface, is perfectly smooth and cushioned with a layer of spongy cartilage. In the normal dog, all of these factors work together to facilitate smooth movement and stability.
A good hip joint has a neat, snug fit between the ball and socket; the head of the femur should not be riding around somewhere in the neighborhood of the acetabulum. CHD occurs when the hip joint loosens. Most of the problems resulting from hip dysplasia are a result of this looseness: a loss of tension in the muscles, connective tissue, and ligaments that should support the joint. Most dysplastic dogs are born with normal hips, but due to genetic and possibly other factors, the soft tissues that surround the joint start to develop abnormally as the puppy grows. The most significant of these changes is that the bones are not held in place but actually move apart. The joint capsule and the ligament between the two bones stretch, adding further instability to the joint. As this occurs, the articular surfaces of the two bones lose contact with each other. This separation of the two bones within a joint, called subluxation, causes all the resulting problems we associate with the disease.
There are infinite variations
of dysplasia, ranging from only very slight dysfunction to complete dislocation.
Consequently, no two dogs will be affected by CHD in exactly the same way.
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