Hip dysplasia is the most common cause of rear leg lameness in dogs. It occurs when the hip’s ball-and-socket joint becomes loose and unstable, eventually resulting in joint damage. In affected dogs, the femur doesn’t fit snugly in the pelvic socket, or acetabulum, because the socket is shallow and poorly developed. Additional joint instability can occur if the pelvic bones grow faster than the supporting muscles, causing arthritis.
Risk factors and detection
Some dogs are genetically predisposed to hip dysplasia, but environment also plays a big role. Large-breed dogs are most often affected, particularly German shepherds, rottweilers, Labrador retrievers, golden retrievers, and Saint Bernards. Small dogs can get hip dysplasia but often don’t show signs of disease.
In genetically predisposed dogs, joint laxity results from joint abnormalities and rapid growth. If the supporting muscles can’t keep up with bone growth, a thriving pup can develop loose joints, which cause additional stress on the hip, abnormal joint structure, and arthritis. Obesity, strenuous exercise, or overfeeding a growing puppy all add to the problem.
Symptoms may develop as early as 4 months of age, but most dogs show signs of lameness at 1 or 2 years old. Dogs with mild hip dysplasia and minimal arthritis may not become lame until they’re 6 to 10 years old. Both hips are affected, but to varying degrees.
Young dogs with hip dysplasia may experience difficulty moving or rising from a lying position or show a reluctance to run, jump, or climb. They may limp or have a "bunny hopping" gait. Older dogs may show lameness (especially after exercise), difficulty rising, stiffness in the hips, or loss of muscle mass in the hind legs as arthritis develops.
Veterinarians sometimes identify loose hip joints in young puppies during physical exams. But doctors typically use X-rays to detect hip dysplasia, and they may sedate the dogs for proper positioning.
An organization called the Orthopedic Foundation of America (OFA) maintains a hip dysplasia registry for purebred dogs. Veterinarians across the country submit X-rays, and the OFA uses them to evaluate dogs for hip dysplasia. The OFA then rates the dogs based on the hips’ appearance. A dog must be 2 years old to qualify for certification, but the organization will screen X-rays for younger dogs. Many breeders use OFA certification to select mates with good hips.
The University of Pennsylvania Veterinary School developed another evaluation method, known as PennHip. The PennHip program uses X-rays to gauge hip laxity, which doesn’t change as dogs age and can be measured in puppies as young as 16 weeks. Based on the X-rays, the university assigns each dog a joint laxity distraction index (DI) number. The PennHip program compares dogs of the same breed, and the program only recommends breeding dogs scoring in the top half of their breed. Dogs scoring in the lower half have a greater chance of developing hip dysplasia.
Prevention and treatment
Both genetics and environment play a role in prevention. Choose a puppy whose parents are rated "Good" or "Excellent" by OFA or certified by PennHip, and don’t breed dogs with hip dysplasia.
Closely monitor your puppy’s food intake so she doesn’t gain weight too quickly. In fact, puppies at risk for hip dysplasia should eat a calorie-controlled diet and avoid vitamin and mineral supplements unless the doctor prescribes them. Your veterinarian can help you determine the appropriate type and amount of food. Dogs less than 12 months old also should avoid strenuous exercise, including excessive jumping.
Depending on the dog’s age and size and the severity of the disease, treatment ranges from pain management to surgery. In mild cases, weight loss and limiting exercise may control the pain. Exercise restriction means walking your dog only on a leash and limiting running, jumping, and playing for as long as she shows signs of pain. Swimming is an excellent exercise that improves muscle mass and joint flexibility without overstressing the hips. Dogs with more advanced disease and pain need additional therapy.
Medical therapy
Nonsteroidal anti-inflammatory drugs (NSAIDs), such as carprofen and etodolac, are the preferred medications for pain and inflammation in dogs. They cause minimal side effects and are very effective. Aspirin also relieves pain in dogs, but it may cause stomach upset or ulcers if used regularly. Over-the-counter pain relief drugs formulated for people can harm your dog, so consult your veterinarian before administering any human medications.
Another group of drugs called chondroprotective agents helps prevent further cartilage damage and promote joint repair. They’re most effective in the early stages of arthritis. Some are nutritional supplements administered orally (glucosamine and chondroitin sulfate), while others are injectable products (polysulfated glycosaminoglycans). Use these treatments only if your veterinarian recommends them.
Surgical therapy
Your veterinarian may recommend various surgical procedures:
- Triple pelvic osteotomy or femoral osteotomy restructure the hip joint and are only useful for young dogs with no arthritic changes in the joint.
- Pectineal myectomy involves removing a hip muscle to relieve tension on the joint. The surgery helps relieve pain in mature dogs, but it won’t slow the progression of arthritis.
- Femoral head and neck removal involves removing the head of the femur, allowing a fibrous union to replace the ball-and-socket joint. It relieves pain and works best in smaller dogs (less than 40 pounds).
- Total hip replacement is the preferred treatment for re-establishing normal, pain-free limb and joint function in mature dogs with severe arthritis. An orthopedic specialist performs the surgery, which involves removing the old joint and replacing it with an artificial joint.
