Hip dysplasia (HD) is a painful condition caused by a malformation of the hip joint. Normally the ball of the femur (the round head at the top of the thigh bone) fits snugly into the socket of the hip (acetabulum), the teres ligament, as well as large muscles, hold the joint in place.
As the cat walks, runs, climbs, lies down, the ball glides smoothly over the socket. However in cats with hip dysplasia, the fit of the femur head into the socket is poor, surrounding muscles may also be weakened, which results in the ball becoming easily displaced from its socket (known as subluxation).
While hip dysplasia is inherited from both of the parents, environmental factors also play a role in the development of this disease, particularly weight gain and nutrition.
The condition is common in dogs and people but rare in cats. It is believed to be inherited, polygenic (meaning more than one gene is involved) and both parents must carry the genes responsible. They may have hip dysplasia themselves or be carriers, meaning they carry the gene, but don’t have the condition. Certain breeds are more predisposed to hip dysplasia, particularly large/heavy boned breeds including Maine Coons, Norwegian Forest Cats, Persians, Himalayans, Exotics and in the smaller Devon Rex. It is believed between 18-22% of Maine Coons are affected. Female cats are more commonly affected than males. Hip dysplasia is usually bilateral, affecting both of the cat’s hips.
The hip joint continues to develop after the kitten has been born and those who carry the defective genes typically show no signs of the condition at birth. Symptoms gradually develop over time and may vary depending on the severity of the disorder as well as the progression and duration of the disease.
Clinical signs tend to appear from 4 – 6 months of age and typically relate to looseness in the hip joint, reluctance to move and pain. Later, as the condition progresses, symptoms of arthritis present.
Limping on one or both hind legs
Weakness in the hind quarters
Reluctance to move
Inability or reluctance to jump
Loss of muscle mass (atrophy) around the hip joint
Swaying of the affected limb when walking (this is known as cow hocks)
Difficulty lying down
Pain when touched
Reluctance to squat when using the litter tray
Over time, wear and tear on the joint can lead to the development of degenerative osteoarthritis. Leading to further pain, stiffness and swelling.
Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you. He will check the range of motion of your cat’s hind limbs.
An x-ray will be performed to evaluate the hip joints. This will be performed while under general anesthetic. X-rays may be sent off to a specialist radiographer for detailed evaluation and to assess and grade the hips.
There is no one type of treatment for hip dysplasia in cats. Treatment depends on the age of the cat and the severity of the condition. Mild cases of hip dysplasia where your cat is showing no signs of pain may not require any treatment at all.
If your cat is overweight, he should be put on a calorie restricted diet, which must be supervised by your veterinarian. The more weight your cat is carrying, the greater the pressure on the joints.
Painkillers may be prescribed to relieve discomfort.
Anti-inflammatories may be provided to reduce inflammation.
Avoiding vigorous exercise, climbing and jumping which may further inflame the problem. Keeping your cat either confined indoors or in a cat run.
For cats who fail to improve after the above treatment options, surgery may be required. The type of surgery depends on the age of your cat and the severity of the condition.
Triple pelvic osteotomy (TPO) – This surgery works best for young cats who have minimal or no degenerative changes to the hip joint. It involves making three incisions in the rump, groin, and hip, the pelvis is then cut in three places and rotated. A plate and screws are used to secure the pelvis in its new position.
Femoral head and neck excision (FHO) – This involves removing the head and neck of the femur, the muscles that hold the joint in place will continue to do so, without the femoral head rubbing on the socket. This surgery is cheaper than a total hip replacement. One leg may be shorter than the other after this surgery and your cat may possibly have a limp, but this should cause him pain or discomfort and he should have a normal range of motion.
Total hip replacement (THR) – This surgery is recommended for older cats who have developed arthritis. It involves replacing the femoral head and socket with a metal and plastic implant.
Recovery after surgery will take several weeks. In this time your cat will need to be confined to a cage or small room. Your cat can expect to be fully restored to proper working order in the hip(s).
How to avoid hip dysplasia?
As this is an inherited, avoid breeding with cats who are known to have or carry the condition.
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