Hip Dysplasia in the Dog

Hip dysplasia is a common inherited problem in dogs but it also occurs in other species. It is primarily a disease of large dogs but can be seen in any breed. The hip is a ball and socket joint. Close relationship of femoral head (ball) and the acetabulum (socket) transfers power from the muscles to drive the body forward for maximum strength  and speed.

The ball rotates freely within the socket and the bones are shaped to perfectly match each other and are covered by a spongy layer of cartilage. The joint is surrounded by a fibrous joint capsule and contains lubricating oil (joint fluid).

Hip dyspasia is an abnormal development of the joint causing a laxity (or looseness) of the joint. As the joint develops the two bones loose contact with each other so the joint can subluxate or partially move out of the socket.  With time the bones become more deformed, the surrounding tissue becomes stretched and the joint becomes progressively unstable and inflammed.  Inflammation leads to the body laying down bony spurs and fibrous tissue around the joint, causing progressive osteoarthritis.

Cause

The cause of hip dysplasia is multifactorial.  It is definitely an inherited disease but can also be influenced by external factors after the puppy is born.  Excessive nutrition, obesity and an inbalanced diet can contribute to it’s development.   In addition over exercise leading to increased force on the hip joint eg jumping, ball chasing, excessive running can increase the chance of it developing.

Signs

Not all dogs will show clinical signs at a young age.  Some dogs only show signs of pain and discomfort as the joint progressively deteriorates with age, after periods of confinement or with obesity.  Clinical signs range from reluctance to jump, lameness, pain on manual manipulation of the joint, a bunny hopping gait, stiffness when getting up or down,  or muscle wastage in the hind quarters.

Diagnosis

Clinical signs may be suggestive of hip dysplasia but before a diagnosis is made you must consult your veterinary surgeon.  Your vet will need to anaesthetise your dog so he/she is relaxed.  Palpation may reveal a degree of hip laxity, but X-rays of  hips is the only real method of diagnosis.  The xray can show the degree of malformation of the joint and will also highlight the degree of secondary arthritis.                                                                 

Treatment

Treatment can be divided into non-surgical and surgical methods:

Non surgical

Aims to alleviate signs and progression of the disease but the deformity and secondary changes will not change significantly.

1. medication to relieve pain and reduce inflammation.
2. Neutroceuticals – nutritional supplements to help repair cartilage damage and reduce inflammation eg glucosamine/chondroitin/omega oils.
3. Weight loss – this is probably one of the most important.
4. Physiotherapy
5. Warm and soft supportive bedding
6. Low impact regular exercise to build muscle strength but minimise trauma.

Surgical

It is beyond the scope of this article to go into detail but some surgical methods available are:

1. Triple pelvic osteotomy – performed in young dogs prior to 10 months of age.  This involves surgically cutting the pelvic lines to realign the joints
2. Total hip replacement. Replacing the affected joint with an artificial one.
3. Femoral head excision arthroplasty.  A salvage procedure to surgically remove the affected ball of the joint so the body forms a fibrous replacement joint.

Prevention

Prevention of hip dysplasia is extremely important, especially with breeding stock as they have the potential to increase the incidence of the disease.  Remember that not all dogs will show clinical signs, so x-ray screening is the only way to determine if dogs have the disease.  There are 2  schemes available in New Zealand. 

1. The New Zealand Veterinary Association Hip Dysplasia scheme. Dogs must be x-rayed under general anaesthesia in a standard view with the hips extended.  One of a panel of veterinary radiologists then assesses the x-rays and give the hips a score out of 108.  This is divided into signs of hip deformity and changes consistent with secondary arthritis.  A score of 0 means the perfect hip – rarely achieved.  An average score for each breed is available and it is important to only breed from animals with a hip score lower than the breed average.
2. Penn hip scheme – a recently available scheme.  The x-ray can only be taken by Penn Hip certified veterinary surgeons and involves taking specialised x-rays that highlights laxity (looseness) of the hip joints.

As previously mentioned a good balanced diet avoiding excessive feeding, plus controlled exercise during the first year of life  are also extremely important to help prevent this disease.