In the world of small animal veterinary medicine, hip dysplasia is considered the mother of all orthopedic diseases. It's very common in large dogs, relatively common in smaller dogs, and it's even seen in cats.
Hip dysplasia is a genetic disease in pets that causes mild to severe changes to the inner workings of the hip joint. More specifically, hip dysplasia is when the femoral head (the ball portion of the femur) and the acetabulum (the pelvis's hip socket) align poorly and are unable to provide the smooth movement a pet requires for a lifetime of weight bearing and normal wear and tear.
Hip dysplasia is painful and expensive to treat and one or both hips may be involved. It's also preventable. But this last point is a complex matter, especially when you consider that hip dysplasia is acquired primarily through hereditary means when an animal (usually a large breed dog) inherits a series of bad genes instructing the body to assemble the hip joint's components (the femur and the pelvis) together poorly.
Symptoms and Identification
The problem with hip dysplasia is that it's not always obvious that your pet has it. Because its severity is variable due to the way this disease is inherited, some pets will show signs as early as four months of age, while others surprise us with symptoms that appear only when they reach middle age or even later.
Crippling arthritis (often referred to as osteoarthritis) is the result in all cases. Because the bones of the hip joint don't line up just right, inappropriate, painful rubbing occurs. The body then attempts to minimize pain by creating bone where bone shouldn't be so as to minimize movement of the joint. Unfortunately, this unwanted process inevitably leads to more pain whenever the pet moves.
Limping is the most obvious sign of hip dysplasia, but as if to confuse us further, is not always present. Loss of muscle mass in one or both thighs, reluctance to jump, a funny way of walking, or slowness in rising can also signal the presence of hip dysplasia.
Standard X-rays are the obvious way to identify the problem once signs occur. But other methods are now widely available to help predict the likelihood that dogs, in particular, will be affected by hip dysplasia (cats, at present, will have to wait for these techniques to become available for them).
The Orthopedic Foundation of America (OFA) will accept your veterinarian's X-rays and make a subjective determination of hip quality. PennHip is another method that more objectively assesses the quality of pets' hips. It's able to accurately predict the severity of a dog's hip disease even when no evidence is immediately evident through other methods.
Giant, large, and dwarfed, small breed dogs are most often affected, but mixed breed dogs and cats are not immune either.
Several studies in veterinary journals have highlighted how common hip dysplasia is across different dog breeds.
In my experience, most clients are unaware of their pets' hip status, especially when pain is not yet obvious to them. That's because dogs don't display pain the same way we humans do. Whining and complaining is just not in their nature. But observant veterinarians will know it's there even before limping and other more obvious signs are present.
By 2 years of age, 95% of animals that have genes for hip dysplasia will show evidence on X-rays. But the severity of the dysplasia as seen on a normal X-ray doesn't always indicate the degree of pain or lameness (limping). It also doesn't tell us when a pet will begin to show signs of the disease.
The PennHip method however can be used to predict whether a given dog is likely to develop hip dysplasia, despite the fact that the OFA method is still more popular among veterinarians and breeders.
One study  also suggests that the OFA percentage of dysplastic hips underrepresents the true percentage in any dog population. The study showed that the prevalence of canine hip dysplasia ranged from 53% to 73% in Golden Retrievers whereas the OFA reports that around 20% show signs of dysplastic hips. If true then the prevalence of canine hip dysplasia may be considerably higher than the OFA percentages suggest.
There are at least as many options for hip dysplasia treatment as there are breeds of dog affected. Sadly, most of them are surgical. Though pain relief through drugs, supplements and weight management (crucial!) can be had, hip replacements for end-stage, severely affected dogs is the most recommended course of action for pets of a certain age and body type. This procedure replaces the ball and socket with artificial components for comfortable movement.
Consult your local, board-certified veterinary surgeon for other alternatives. If detected at a young enough age (and for certain dogs), hip dysplasia may be amenable to less-invasive surgical intervention. Here are some common alternatives your surgeon may consider:
Triple Pelvic Osteotomy (TPO): This method is best for dogs that have been diagnosed with hip dysplasia before major signs are present (puppies, in particular). It cuts the pelvis in three places so that the ball of the femur lines up better with the socket of the hip joint.
Femoral Head Osteotomy (FHO): This approach cuts off the head of the femur, preventing painful rubbing in the joint and allowing the muscles in the area to pick up the slack. Again, the FHO is best for pets that still have a lot of muscle in the area. In other words, these candidates don't yet have major changes due to hip dysplasia.
Personally, I believe all these patients are best served by a board-certified veterinary surgeon. These professionals are best trained to determine the kind of procedure your pet needs and, by virtue of their unique training and experience, they have the best success rate in surgically addressing these cases.
Wow--what a range! If a pet requires a bilateral (both sides) hip replacement, you're looking at $7,000 to $12,000 of surgery. For all other kinds of surgeries, $1,500 to $3,000 per hip is the norm. But remember, the particular veterinary hospital's costs, its geographic location, and the quality of the surgeon may well dictate an even higher price. That's why board-certified surgeons will almost inevitably provide higher-end estimates for hip dysplasia treatment.
Beyond surgery, a lifetime of pain-relieving medications and supplements has a way of adding up. Assume the following will be in order, at least intermittently, for all hip dysplasia sufferers.
Glucosamine and fatty acids are commonly recommended nutraceuticals (dietary supplements) for all pets with any kind of joint disease. They work to protect the cartilage in the joint.
Pet-specific anti-inflammatory medication like carprofen (Rimadyl) and meloxicam (Metacam) may also be prescribed.
As an adjunct to these, human opiates like tramadol (Ultram) may be in order
The onus for prevention is primarily on the breeders of dogs. Those who responsibly breed will seek OFA certification or PennHIP evaluation for their breeding dogs. They will not breed any dogs who suffer even mild forms of this disease, as the genetic transmission of severe forms can occur even through mildly affected parents.
Those who are in the market for puppies are similarly advised. For those of you who intend to purchase or adopt dogs of a breed affected by hip dysplasia, such as those above, you should request OFA or PennHIP certification of the parents.
 Journal of the American Animal Hospital Association 2002; 38:467 - 477. Breed Susceptibility for Development Orthopedic Diseases in Dogs
 JAVMA, Vol. 226, No. 3, Estimates of prevalence of hip dysplasia in Golden Retrievers and Rottweilers and the influence of bias on published prevalence figures
 Orthopedic Foundation for Animals