What is it?
Hip dysplasia is a condition characterised by malformation of the hip joints, which leads to rapid degenerative changes (typically early-onset arthritis). It is a genetic condition that used to be present in many breeds; due to the BVA/KC Hip Scoring Scheme it is gradually becoming less common, but it is still one of the commonest causes of hindlimb lameness in dogs.
What causes it?
It is a genetic disorder caused by the interaction of many different genes. In addition, the severity of symptoms will often depend on the environment the dog lives in, and even how they grew up. In most cases, it causes the "socket" (acetabulum) of the hip joint to be too shallow, so the "ball" (the femoral head) keeps popping out. This causes stress on the joint, resulting in further deformity and, ultimately, early onset osteoarthritis in the hips.
What dogs are at risk?
It is typically seen in large-breed dogs, but other breeds may also be affected. The highest risk breeds include St Bernards, German Shepherds, Labradors and other Retrievers. The incidence in Setters used to be very high, but a strict breeding programme appears to have reduced it substantially.
Dogs with hip dysplasia are often also at risk of elbow dysplasia.
What are the symptoms?
Although the condition begins in the immature dog, in many cases symptoms will not be apparent until later (although very severe cases may show as early as 4 months). Classical symptoms include decreased willingness to run, climb stairs and slopes, or jump; difficulty getting up after lying down; and intermittent hindlimb lameness. The condition usually affects both hips (although one may be worse), so it is not uncommon for the dog to be lame on different sides on different occasions, depending on which one hurts more that day. In addition, dogs often adopt a "Marilyn Monroe" type gait, with a narrow-based stance as they try to keep their legs tightly together to reduce the chance of their hip popping out of joint. Other dogs may adopt a "bunny-hopping" or swaying way to get around, because this puts less pressure on the painful joints.
How is it diagnosed?
Clinical examination is highly suspicious, but X-rays of the hips are diagnostic.
How can it be treated or managed?
Unfortunately, there is no way to restore normal hip structure in these dogs. However, most dogs can live relatively normal lives if the arthritis can be controlled (for example, with anti-inflammatory drugs and painkillers). In more severe cases, surgical reconstruction (e.g. triple-pelvic osteotomy) or removal of the hip joint (e.g. excision arthroplasty) can render the affected joints pain free. However, the "gold-standard" treatment for a dog who cannot be kept comfortable with medical treatment is a hip replacement, where the affected joints are replaced with artificial ones. This is estimated to be successful in over 90% of cases.
Can it be prevented?
Only by attempting to breed the relevant genetic traits out of breeds - the Hip Scoring scheme is designed to identify those dogs with "bad genes" which should not be bred from, and those with "good genes" that should be prioritised.