Hip dysplasia is a disorder of the hip joint which begins during the growing stage in puppies and which is strongly influenced by inherited and environmental factors. It can cause spontaneous lameness of the back legs in a proportion of affected dogs. The condition often affects both hips, although lameness may be seen in only one leg. Giant, large and medium sized breeds are most commonly affected although the problem may be seen in small breeds.
In the normal canine hip joint, the head of the thigh bone (femur) fits tightly into the deep socket in the pelvis (acetabulum). The femur head should sit within the acetabulum so that more than 50% of its surface is snugly contained. Hip dysplasia describes malformed joints which are loose fitting (lax). This laxity results in an unstable gait, and the head of femur rubs unevenly against the rim of the pelvic socket. The joint cartilage is then subject to excessive "wear and tear"and the joint capsule lining becomes inflamed and painful. These processes result in deformity of the bones and arthritis develops.
Detecting the signs
One of the main problems in detecting hip dysplasia is that some dogs with abnormal joints do not show any lameness and apparently walk with a normal gait. Lameness is only apparent if the joint is sufficiently unstable or painful to enforce a change in gait and may relate to the age of the dog as well as the severity of the condition. Potentially dysplastic hips are probably normal at birth but deteriorate as the animal grows. Signs of lameness appear as the puppy becomes more active. It will not move as freely as normal dogs and often "bunny hops" when trotting -as this allows it to shift weight off the painful back leg on to the front legs. Affected puppies prefer to sit rather than stand and have difficulty with stairs. When walking they may have a marked sway with the pelvis appearing to rise and fall with each step. Puppies suffering from severe dysplasia may not be able to move faster than a painful walking pace. Hip dysplasia progresses significantly between 6-18 months of age with most of the changes developing before the animal is 2 years old. In adult dogs the changes that began in early life may result in hip arthritis in middle or old age. The dog will then become lame even though no signs were noticed when it was a puppy.
Genetic and environmental factors influence the development of hip dysplasia and affect the final degree of lameness and disability.
The environmental factors of most importance are:
- Feeding a diet that results in excessively heavy puppies at a young age. This leads to overloading of the soft cartilage of the developing joint and a resulting deformation of the predisposed dysplastic joint
- Overexercise of dogs with unstable joints will exacerbate any wear and tear of the hip.
Various methods of treatment are available for hip dysplasia.
Rest and anti-inflammatory drugs will often help dogs showing pain after exercise. Lead walks which are short but frequent -10 minutes 4 times a day - will allow the growing skeleton to adapt and the joint to become more stable and painfree by the time the dog becomes mature at about 15 months of age. This is greatly helped by keeping the dog slim and not allowing it to grow too fast. This conservative treatment is successful in about 60-70% of cases and the dog can then be allowed to become more active. Dogs with severe signs that do not respond may need corrective surgery which may take many forms. In young dogs, realignment of the hip joint components can be performed by cutting the bones and adjusting them with steel plates and screws. For older dogs, a total hip joint replacement in which the femur head and acetabulum are replaced by a stainless steel prosthesis which fits into a plastic socket can be performed. These operations are costly and have to be carried out at veterinary referral centres.
The main way of preventing a puppy from having hip dysplasia is to breed only with unaffected dogs. Any animal of a suseptable breed should be x-rayed before being mated. The xrays are examined by a panel of experts and allocated a score - the lower the better. At the Heath Veterinary Group we are well equipped to take Hip Dysplasia xrays of even the largest dogs.
Making sure the diet is right is very important. Large breeds should be fed a diet specifically for them. This will control the puppies rate of growth, reducing the stress on the immature joints.