Hip Dysplasia occurs when a hip socket forms abnormally. It can range in severity and in severe cases dogs can become lame.

It is caused by a polygenetic trait, which means that it is more complex than just a single gene. HD is thought to be genetic, but also can be triggered by environmental factors.

HD can cause repetitive strain injuries and micro-fracturing of the bone and cartilage within the hip. (Source: Fitzpatrick Referrals) These can cause pain to the animal affected.

DIAGNOSIS
When a dog has symptoms of HD, diagnosis can be achieved through X-Rays. These X-Rays are usually done using sedation.

The main symptoms of HD are:

• Decreased activity

• Decreased range of motion

• Difficulty or reluctance rising, jumping, running, or climbing stairs

• Lameness in the hind end

• Looseness in the joint

• Narrow stance

• Swaying, “bunny hopping” gait

• Grating in the joint during movement

• Loss of thigh muscle mass

• Noticeable enlargement of the shoulder muscles as they compensate for the hind end

• Pain

• Stiffness

          Source: American Kennel Club


TREATMENT
There are both surgical and non surgical options to treat hip dysplasia, and the treatments used are decided on a case by case basis. Possible treatments involve physical therapy, anti-inflammatory drugs (such as NSAIDS) or even surgeries such as ostectomies and hip replacements.

PREVENTION
Although some cases of HD can not be prevented, managing your puppy or dog's environment can reduce the risk of the disease.

The following are generally seen as good ways to reduce the risk of HD:

• Feed your puppy an appropriate and balanced diet suitable for puppies of that size. Large breed puppies need to grow at the right rate to avoid asynchronous growth and rapid growth rates, which can cause issues with joints and diseases such as developmental orthopedic disease (DOD) and HD. This can be managed with a size / breed appropriate diet, which will have the correct ratios of fat, protein, calcium, and other nutrients such as phosphorous. (Sources:  University of California, VCA Hospitals, Cummings Veterinary Medical Center, American Kennel Club.)

• Providing exercise and keeping your puppy a healthy weight. Puppies should not have a strenuous exercise program until their joints are developed later in life. Puppies benefit from 'free running' - allowing them lots of time to play outside and set their own pace.

• Purchasing a puppy that is from hip scored parents, or from lines where there have not been hip issues diagnosed (the safest way to ensure this is to search for dogs in your prospective puppies' pedigree on databases such as OFA or Pennhip, if you live in America.)

HIP SCORING
A dog's hips can be scored and graded when they reach a mature age. In the UK, each hip is scored as a measure of dysplasia. 

The hips are graded by an x-ray of the hips, which are studied by a panel of experts.

The following is a table of corresponding grades across different countries, for comparison. This table was produced by the BVA (British Veterinary Association)  .