Hip dysplasia is the most commonly inherited orthopedic disease is dog. It affects all dogs with some breeds more affected than others. Large and giant breeds seem to have more problems with hip dysplasia but we can and do see it in small and toy breeds as well as cats.
Hip dysplasia is the abnormal or faulty development of the hip. This causes excessive wear on the joint cartilage and eventually leads to the development of osteoarthritis (OA). There are multiple factors that lead to dysplasia including multiple genetic factors and environmental factors (ie. weight, age).
The clinical signs associated with hip dysplasia are the result of the formation of osteoarthritis(OA). The severe form of the disease can present as early as 5-12 months of age. There is overt pain, lameness, low exercise tolerance, reluctance to jump or climb stairs. You may hear a “click” when your pet is walking and muscle atrophy (decreased muscle mass) may be visible in the thigh muscles of the rear limbs. Clinical signs in the milder, chronic form of hip dysplasia develop later in life and may initially present as mild discomfort and stiffness. This can progress to more severe pain, difficulty getting up, hesitance with stairs and jumping and there is often a crepitus (a grating sound produced but the friction between bone and cartilage) and decreased range of motion in the hips.
There is no cure for hip dysplasia and the resulting OA. Non surgical treatment options include medication to reduce pain and inflammation (NSAIDS), nutraceuticals, nutritional management, modified exercise plan and physical therapy. End stage disease management may include surgery.
The first step in battling OA is identifying the presence of hip dysplasia. In the early 1980’’s through a scientific study, it was determined that hip joint laxity (the looseness of the hip) is the most important risk factor for the development of OA. The looser the hip, the more likely OA will develop. This lead to the development of the Pennsylvania Hip Improvement Program (PennHIP). It is a measure of hip joint laxity. Through a series of 3 different radiographs, we can determine the distraction index (DI) which is a measure of laxity in the hips. The DI ranges between 0.2 -1.0. The closer DI is to 0.2, the tighter the hips.
PennHIP can be performed on all breeds as early as 16 weeks of age. This allows early identification so nutritional and behavioral modification can begin at that time which can delay the onset of OA. For those dogs that are bound for the show ring, agility trials or on the path to be a working dog, PennHIP can identify the best candidates for these endeavors. PennHIP results are an objective, repeatable evaluation of hip joint laxity.
Many of you may have heard of OFA (Orthopedic Foundation of Animals). In the past, this was the gold standard for hip evaluation. But using this method of evaluation has not reduced the incidence of of hip dysplasia in dogs. This means that the test is not identifying dogs with hip joint laxity. It is a subjective evaluation that has been proven to change based on the evaluator. It is also possible to mask laxity in the joint leading to perpetuation of hip dysplasia if these dogs are used for breeding. PennHIP avoids these pitfalls but providing an objective evaluation of laxity that is repeatable over time and different evaluators. It is also a much earlier identification as opposed to OFA which will not evaluate a pet before 2 years of age.
So what does this mean for the pet owner?
If you are planning on breeding, doing agility/obedience events or your dog is slated to be a working dog (therapy, police work, protection) early identification aids in selection of sound individuals. This can save time and money spent on individual animals that have a greater likelihood of developing OA. Breeders can also make changes (for the better) by breeding dogs with tighter hips. Depending on the selection pressure, significant changes in the genetics of a breed can be made.
If your pet is primarily a companion, identification of dogs with loose hips can aid in the development of a dietary and exercise program to slow the progression of the disease and delay the onset of clinical signs/pain associated with OA.
PennHIP evaluation requires 3 different radiographs that are taken with the pet under deep sedation. All films are then submitted to the PennHIP organization for evaluation and determination of the DI (distraction index). A report is generated by the organization and if the dog is a purebred, it is ranked among other dogs of the same breed. A discussion of the results and implications with one of our veterinarians ensues.
If you are interested in PennHIP for your dog or you have any questions, contact the hospital. We will be happy to answer all of your questions.