Hip Dysplasia in Dogs

Hip dysplasia in dogs is a genetic disease and is the most common cause of dog hip pain and rear leg lameness in dogs. This page looks at the causes, symptoms, and treatment of canine hip dysplasia.

Dog Hip Joint

The hip is a ball-and-socket joint. The bones of the dog hip joint include the femur (specifically the femoral head - the ball) and the "bony pelvis" (specifically the acetabulum - the socket). In a normal hip joint, the ball and socket fit snugly together. The two bones are held together by a ligament, a joint capsule, and the hip muscles.

What is Hip Dysplasia in Dogs

Dysplasia means "abnormal development". Canine hip dysplasia is a genetic disease that is characterized by an abnormal development of the hip joint. Hip dysplasia in dogs is the most common cause of dog hip pain and hind-leg lameness. It is also a common cause of osteoarthritis in the dog hip joint.

In a dysplastic hip, the femoral head fits loosely into a poorly developed, shallow acetabulum. In dogs younger than 18 months of age, if the bones of the hip are improperly shaped, the ball-and-socket joint becomes loose, which may lead to joint cartilage damage and eventually osteoarthritis.

Specifically, the femoral head (the "ball") may move out of the acetabulum (the "socket") as the dog walks or runs. This condition is called subluxation. In the worst cases, the femoral head may come completely out of the acetabulum - a condition called luxation.

Most dogs with hip dysplasia only have subluxation, which over time leads to cartilage destruction and malformation of the hip joint as the dog grows.

[Top of Page]

Two Stages of Hip Dysplasia in Dogs

Canine hip dysplasia can be considered as a two-phase disease with two different causes of pain.

The first cause of pain is subluxation of the hip joint, which stretches and tears the soft tissues around the joint. In many cases, this pain eases as the dog grows because the joint "scars down" and tightens. Therefore, young adult dogs may show a remission of clinical signs such as hip joint pain even without treatment.

The second stage of hip dysplasia is the arthritic stage. Although the joint is no longer loose or subluxating, the hip joint itself is still not normally formed (not a perfect ball-and-socket joint as in normal dog hip joints). Consequently, there is increased wear and tear and this leads to the destruction of cartilage, which eventually results in osteoarthritis and hip joint pain.

[Top of Page]

Causes of Hip Dysplasia in Dogs

As mentioned above, canine hip dysplasia is a genetic disease. It occurs most commonly in large breed dogs, including the St. Bernards, Newfoundlands, Rottweilers, Chesapeake Bay Retrievers, Golden Retrievers, German Shepherds, Labrador Retrievers, and others. Sometimes, it occurs in smaller breed dogs as well, but such dogs are less likely to show symptoms.

There are also risk factors that may aggravate or accelerate hip dysplasia in dogs, although these factors by themselves cannot cause the disease:

Diet: It has been found that feeding a very high calorie diet to growing puppies can worsen or accelerate hip dysplasia, because the rapid weight gain places increased stress on the hips. As well, a diet with an imbalance of calcium and phosphorous is bad for bone development.
Weight Problem: Being overweight also supports the genetic potential for hip dysplasia in dogs, as the extra weight puts increased stress on the dog's joints.
Improper Exercise: Inappropriate exercise during the growing phase of a puppy can also bring on the symptoms of hip dysplasia. Inappropriate exercise include jumping up and down from heights and landing on the puppy's hind legs, standing up on their hind legs, and running on pavement.

[Top of Page]

Symptoms of Hip Dysplasia in Dogs

Dogs with hip dysplasia are born with hips that appear normal but progressively structural changes will occur. The age of onset is 4 to 12 months.

Puppies with hip dysplasia will show hip pain, limp or have a swaying gait, bunny hop when running, and have difficulty in the hindquarters when getting up.

Lying on his back, an affected puppy may not extend his rear legs into the frong-leg position without experiencing pain.

However, not all puppies with hip dysplasia will experience pain. In fact, many dogs with this condition never show a sign of pain during their entire lifetime. Some dogs will have transient signs of pain caused by the subluxation but never show pain due to arthritis, while others will improve after the early stage and not show signs of arthritis for many months or years. But in most cases, dogs with hip dysplasia will show signs of hip arthritis during their middle or later years.

[Top of Page]

Diagnosis of Hip Dysplasia in Dogs

Diagnosis of canine hip dysplasia is by palpation and X-rays.

In a young dog, through palpation the veterinarian may feel the joint subluxation, as well as muscle loss and pain on extension of the hip joint.

There are several ways for getting X-rays of the hips for examination.

The most basic way is to lay a heavily sedated dog on his back with the legs extended. An X-ray obtained this way is referred to as the OFA view. It is the view used by the Orthopedic Foundation for Animals (OFA) to grade the severity of the disease in dogs older than 2 years of age, and dysplastic hips are rated Mild, Moderate, or Severe. If the findings are not clear, the hips are rated Borderline.

Mild: X-rays of mild hip dysplasia will show mild subluxation with the hip ball part-way out of the socket. There are no visible arthritic changes.
Moderate: X-rays of moderate hip dysplasia will show the hip ball barely seated into a shallow acetabulum. Arthritic changes such as wear and flattening of the femoral head, a rough appearance of the joint surfaces, etc. will also show.
Severe: X-rays of severe hip dysplasia will show the femoral head completely out of the joint and arthritic changes are marked.

Another way to evaluate hips is called the PennHip method, developed at the University of Pennsylvania Veterinary School. PennHip X-rays are taken using the OFA views, but additional views are taken by applying gentle force to evaluate joint laxity and to determine the severity of subluxation.

[Top of Page]

Treatment of Hip Dysplasia in Dogs

Treatment includes medical therapy and surgery.

Medical treatment is similar for younger and older dogs and involves the use of pain killers such as NSAIDs (e.g. Rimadyl), and a joint supplement such as glucosamine and chondroitin for dogs. Weight control and exercise management are also important. Dysplastic dogs should not be allowed to run, jump, or play as long as they show pain.

Surgery options differ from dog to dog, depending on age. The basic categories of surgical procedures include:

Modification of the joint: Young growing dogs without significant osteoarthritis can benefit from this procedure. It is done to try to improve the joint and stop the subluxation. It involves twisting the acetabulum by cutting and rotating the bone, resulting in decreased subluxation and less pain. It can also decrease the progression of arthritis later in life. For puppies under 20 weeks of age, this can be achieved with a technique called juvenile dysplasia symphysiodesis. In older dogs, a surgical procedure called triple pelvic osteotomy (TPO) is required, which involves cutting the pelvis in three places to permit rotation of the acetabulum.
Removal of the joint: For dogs with severe cases of hip dysplasia with luxation or severe arthritis, removal of the joint may be necessary. This procedure is called a femoral head (and neck) ostectomy (FHO), in which the femoral head is removed so that the femur and the pelvic bone no longer make contact. The femur and the leg are supported by the strong muscles surrounding the hip joint. Smaller dogs tend to have better outcomes than larger dogs, although with after-surgery rehabilitation together with weight control, the outcome of FHO can be improved dramatically in larger dogs as well.
Replacement of the joint: Dogs with severe cases of hip dysplasia may also be treated by a procedure called total hip replacement (THR), which involves replacing both the femoral head and the acetabulum with high-grade implants (similar to those used in people). However, this procedure is expensive.