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Hip dysplasia is a hereditary disease that, in its more severe form, can eventually cause crippling lameness and painful arthritis of the joints. It is caused by a combination of genetic and environmental factors. It can be found in many animals and occasionally in humans, but is most commonly associated with dogs, and is common in many dog breeds, particularly the larger breeds.

Hip dysplasia is one of the most studied veterinary conditions in dogs, and the most common single cause of arthritis of the hips

Causes and Effects

In dogs, there is considerable evidence that genetics plays a large role in the development of this defect. There might be several contributing genetic factors, including a femur that does not fit correctly into the pelvic socket, or poorly developed muscles in the pelvic area. Large and giant breeds are susceptible to hip dysplasia, and Cocker spaniels and Shetland sheepdogs are also known to suffer from it.

To reduce pain, the animal or person will typically reduce their movement of that hip. In animals this may be visible as “bunny hopping”, where both legs move together, or less dynamic movement (running, jumping), or stiffness. Since the hip cannot move fully, the body compensates by adapting its use of the spine, often causing spinal, stifle (a dog’s knee joint), or soft tissue problems to arise.

In dogs, the problem almost always appears by the time the dog is 18 months old. The defect can be anywhere from mild to severely crippling. It can cause severe osteoarthritis eventually.

Symptoms

Dogs might exhibit signs of stiffness or soreness after rising from rest, reluctance to exercise, bunny-hopping or other abnormal gait (legs move more together when running rather than swinging alternately), lameness, pain, reluctance to stand on rear legs, jump up, or climb stairs, subluxation or dislocation of the hip joint, or wasting away of the muscle mass in the hip area. Radiographs (X-rays) often confirm the presence of hip dysplasia, but radiographic features may not be present until two years of age in some dogs. Moreover, many affected dogs do not show clinical signs, but some dogs manifest the problem before seven months of age, while others do not show it until well into adulthood.

In part this is because the underlying hip problem may be mild or severe, may be worsening or stable, and the body may be more or less able to keep the joint in repair well enough to cope. Also, different animals have different pain tolerances and different weights, and use their bodies differently, so a light dog who only walks, will have a different joint use than a more heavy or very active dog. Some dogs will have a problem early on, others may never have a real problem at all.

Each case must be treated on its own merits, and a range of treatment options exist.

Diagnosis

There are several standardized systems for categorising dysplasia, set out by respective reputable bodies (Orthopedic Foundation for Animals/OFA, PennHIP  British Veterinary Association/BVA). Some of these tests require manipulation of the hip joint into standard positions, in order to reveal their condition on an X-ray, and since this is very painful and must be held still for a clear image, often the animal will be anaesthetised or sedated to achieve clear diagnostic results.

It is important to note that a dysplastic animal has probably lived with the condition since it was only a few months old, and has therefore grown up taking the chronic pain for granted and have learned to live with it. Dogs suffering such pain do not usually cry out or show it. Sometimes, they will suddenly and abnormally sit down when walking, or suddenly refuse to walk or climb objects which they usually would, but this can equally be a symptom of many other things, including a thorn in the paw, or a temporary muscle pain. So pain recognition is less common a means of detection than the visible gait and other abnormalities described above.

Prevention

Overfeeding puppies and young dogs, particularly in the giant breeds, might aggravate the problem or bring it on earlier, because pups tend to be more active, less aware of their physical limitations, and have immature bones and supporting structures carrying their weight.

Dogs from breeds which are known to be prone to dysplasia can be kept slightly leaner than normal until around 2 years old, by which time the bones are full strength and the animal can be easily brought up to its normal adult weight. Overexercising young dogs, whose bones and muscles have not yet fully developed, might also be a contributing factor.

Responsible breeders who track the incidence of hip dysplasia have been able to reduce the incidence in some breeds but not to eliminate it altogether.

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