Canine Hip Dysplasia
The word dysplasia stems from the Greek words dys,
meaning “disordered” or “abnormal”, and plassein meaning “to form”.
The expression hip dysplasia can be interpreted as the abnormal or faulty development of the hip. Abnormal development of the hip causes excessive wear of the joint cartilage during weight bearing, eventually leading to the development of arthritis, often called degenerative joint disease (DJD) or osteoarthritis (OA). The terms DJD, arthritis and osteoarthritis are used interchangeably.
Canine Hip Dysplasia (CHD) was first described in 1935 by Dr. Gerry B. Schnelle. Dr. Schnelle initially called it “bilateral congenital subluxation of the coxofemoral joint”. It was originally thought to be a rare condition but is now recognized as the most common orthopedic disease in dogs. This radiographic image is the first known example of CHD to be published in a scientific journal.
In 1966, Henricson, Norberg and Olsson refined the definition of CHD describing it as: “A varying degree of laxity of the hip joint permitting subluxation during early life, giving rise to varying degrees of shallow acetabulum and flattening of the femoral head, finally inevitably leading to osteoarthritis.”
Today, the general veterinary consensus is that hip dysplasia is a heritable disease manifested as hip joint laxity that leads to the development of OA. So a knowledge of hip joint laxity is key to predicting the ultimate development of the OA of CHD.
Canine Hip Dysplasia afflicts millions of dogs each year and can result in debilitating orthopedic disease of the hip. Many dogs will suffer from osteoarthritis, pain, and lameness, costing owners and breeders millions of dollars in veterinary care, shortened work longevity, and reduced performance. The occurrence of CHD is well documented in large and giant breed dogs, but there is also evidence that CHD is prevalent in many small and toy breeds as well as in cats.
Hip dysplasia is a disease of complex inheritance, meaning it is caused by many genes and its expression can be affected by multiple non-genetic factors. Veterinarians and dog breeders have attempted to eliminate CHD through selective breeding strategies based on scoring of the standard hip-extended radiograph, however, the reduction of CHD frequency in pure-breed dogs has been disappointing.
Fast facts about Canine Hip Dysplasia
- Canine hip dysplasia (CHD) is the most commonly inherited orthopaedic disease in dogs.
- CHD is a degenerative, developmental condition, leading to painful hip osteoarthritis, stiffness, and diminished quality of life.
- All dog breeds are affected by the disease: in some breeds more than 50% of dogs are afflicted.
- The disease is polygenic and multifactorial meaning that CHD expression is a product of both genes and environmental factors such as body weight and age.
- There is no medical or surgical cure for CHD.
- CHD is a major concern for working dog agencies, pet owners, dog breeders and veterinarians.
A developmental disease is not present at birth but develops with maturation and age. The series of radiographs below illustrate how a loose hip gradually develops osteoarthritis (OA).
There is an acute and a severe form of CHD. An affected dog may have one or any combination of the following clinical signs:
Severe (Acute) Form
- Presentation at five to 12 months of age,
- Overt pain, lameness, and functional deficits (low exercise tolerance, reluctance to climb stairs),
- Other signs: audible “click” when walking, increased intertrochanteric width (“points of hips” are wider than normal), thigh muscle atrophy.
Mild (Chronic) Form
- Clinical signs ranging from none to mild,
- Mild discomfort and stiffness in geriatric years,
- Possible pain and crepitus on range of motion.
Clinical signs by themselves do not necessarily mean that a dog has hip dysplasia, other conditions of the hip or knee can mimic CHD. A radiograph is essential for a more accurate assessment of a dog’s hip joint integrity.