(taken from Sirius Dog.Com)
Canine hip Dysplasia (CHD) is caused by a loose hipbone-thighbone connection. It leads to hind-end pain and lameness that can range from mild to crippling. CHD is genetically transmitted. But because multiple genes are involved, scientists have yet to unravel the pattern of inheritance. Adding to the CHD riddle is the complicated interplay between heredity and the environment. Environmental factors (such as growth rate) influence whether CHD shows up clinically during a dog's life.
Although the disease disproportionately affects larger-breed dogs, veterinarians have documented hip dysplasia in just about every type of dog, including mixed breeds. The good news is that owners and breeders can take preventive measures to reduce the odds of a dog developing hip dysplasia. But if your dog does develop CHD, early detection and treatment can help your friend live a long and relatively comfortable life.
Remember the lyrics, "The hipbone's connected to the thighbone"? To picture the dog's hip joint, imagine a ball fitting into a socket. The ball is the top (head) of the thighbone (femur), which is coated with a smooth, low friction surface of cartilage. The femoral head fits into the hip's socket (acetabulum). The entire ball-and-socket joint is surrounded and supported by muscles, ligaments, and lubricating synovial fluid.
During the growth spurt from birth to 60 days, the dysplastic puppy's muscle and connective tissue--unlike a normal pup's -- can't keep pace with the fast-growing bones. The resulting mechanical looseness of the joint (hip laxity or subluxation) causes abnormal wear on the cartilage that line the femoral head. As the bone-buffering cartilage deteriorates, arthritis often sets in. "Arthritis is basically an abortive attempt by the body to stabilize the joint by adding bone." explains Dr. Randy Boudrieau, associate professor of surgery at Tufts University School of Veterinary Medicine.
Although pain and restricted range of motion are universal signs of CHD, other indicators may vary, depending on the age of the dog and the degree of arthritis present. In younger prearthritic dogs with CHD, you may hear a "click" as the dog walks. (The femoral head is "popping" in and out of the acetabulum.) Also, young dysplastic dogs often move both back legs simultaneously in a "bunny hop" gait. On the other hand, some younger dogs with radiographic (X-ray) evidence of CHD maintain normal mobility and show signs of CHD only as they grow older and develop arthritis.
Older dogs suffering from CHD related arthritis often rise stiffly after napping or limp after running. They may balk at climbing stairs, jumping into the car, or (dare we say) hopping onto the bed. But both older and younger dysplastic dogs seem to suffer the most discomfort in cold, damp weather.
Although CHD may remain clinically "hidden" in some dogs, early detection is crucial. But how do you detect what is not obvious? A thorough physical examination is the first step. Your veterinarian will observe your dog as it sits, stands, and walks to check for characteristic CHD signs such as a side-to-side swinging gait, lameness, and arched back (caused by shifting weight forward), or overdeveloped front-leg and shoulder muscles.
The veterinarian will next move the dog's hip joint to assess its range of motion and check for pain with the joint extended. The veterinarian will also listen for the "click" of the hip popping out of joint and for the grating sound of bone on bone (crepitus) that indicates cartilage loss.
Finally, your veterinarian may radiograph the hip joint to confirm subluxation or arthritic degeneration. He or she may send the X-rays to the Orthopedic Foundation for Animals (OFA) or to PennHIP for evaluation.
The bottom line is if you discover dysplasia early, you can take action to minimize discomfort. (It is important to point out the veterinary surgeons perform some types of CHD surgery only on dogs that are arthritis-free.) And, of course, knowing early on whether your dog has hip dysplasia con help you make appropriate breeding decisions.
If all the evidence points to CHD, don't despair. Various medical and surgical approaches can ease discomfort and restore mobility. Medical treatments such as weight loss, moderate exercise, and medication aim to alleviate pain and inflammation in and around the joint. But if medical treatment fails to improve your dog's condition, orthopedic surgery may be worth considering. Veterinary surgeons can repair, replace, or remove some of the mechanical defects caused by dysplasia.
Most veterinarians initially suggest a three-pronged medical approach. First and foremost, try to help your dog lose excess weight. "The heavier the animal, the greater the forces acting on the joints," explains Dr. Boudrieau.
Second, moderate your dog's activity. Taking into account its physical condition and pain threshold, arrive at a happy medium---somewhere between complete exercise restriction (inadvisable because it adds to pain and stiffness) and unlimited physical activity. The owner must determine an appropriate activity level and help the dog stick to it.
Even with weight loss and controlled exercise, though, many dogs with CHD have "bad days." To help dogs get through flare-ups, veterinarians usually recommend a weight-based dose of anti-inflammatory medication----usually buffered aspirin. (When giving your dog anti inflammatory medication, restrict it from exercise.) But "a dog's stomach is not quite as hardy as a person's," explains Dr. Boudrieau, so avoid long-term aspirin use, which can cause vomiting and internal bleeding. Because of potential toxicity and side--effects, veterinarians rarely prescribe medications containing acetaminophen, ibuprofen, or corticosteroids for dysplasia.