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Hip Dysplasia

Updated: Apr 25, 2022

What is Hip Dysplasia?


Hip dysplasia is an abnormal development (dysplasia) of the hip joint. It is usually a mismatch between skeletal and soft tissue growths. Typically it affects the hip joint of medium and large breed (usually pedigree) dogs and is a common and often debilitating joint disease. It is genetically mediated and influenced by environmental factors, e.g. breed, rate of growth, type of feeding, other co-existing skeletal disorders, e.g. lumbosacral deformities, spinal disease, trauma, bone or joint disorders of forelimbs, the level of exercise given to young growing dogs of larger breeds.

3D illustration of Canine degenerative joint disease
3D illustration of Canine degenerative joint disease

It causes instability of the joint, pain, lameness in the young dog and arthritis in later life. Hip dysplasia occurs when the hip's ball-and-socket joint does not fit together properly. This results in friction, which damages the surfaces of the joint, leading to pain and eventually arthritis.

How is a normal hip joint?


The normal hip joint is a smooth fitting ball-and-socket joint with the smooth top of the thigh bone fitting firmly into a cup-shaped dent in the pelvis. The fundamental cause of hip dysplasia is a laxity of the soft tissues supporting the hip joint. This causes the joint surfaces to rub against each other instead of gliding smoothly over one another. Hip dysplasia is present from a very young age when the bones are still not fully developed and therefore soft. The hip joint fails to develop properly, and abnormal stress on the joint causes the formation of arthritic new bone. The process becomes a vicious circle, exacerbated by obesity and over-exercise.

What is an inherited joint disease?


Inherited diseases are commonly passed from parents to their offspring and are genetically determined. Puppies inherit the tendency to develop a particular disease, the severity of which may be influenced by factors in its upbringing, such as feeding and exercise. Inherited diseases are more common in pedigree dogs than in cross breeds, with some conditions being more common in some breeds than others. Special scoring schemes have been developed for some inherited conditions. These allow the early detection of the inherited condition so that the individual can be treated and prevent the affected animal from being used for breeding and passing the condition on to its puppies. The best known inherited joint disease is hip dysplasia.

What are the clinical signs of hip dysplasia?


Clinical signs include one or more of the following:-

  1. Pelvic limb stiffness

  2. Difficulty rising

  3. Swaying gait in a young dog.

  4. Sudden onset, uni- or bilateral hind-limb lameness in pups of less than 12 months of age, with pain especially on extension with or without abduction:

  5. Unwilling to jump or climb stairs.

  6. Marked exercise intolerance.

  7. Bunny hopping' gait - bilateral condition.

  8. Kyphotic posture (Hunchback [kyphosis] usually refers to an abnormally curved spine)

Old male Chihuahua dog with hip dysplasia
Old male Chihuahua dog with hip dysplasia

9. Degenerative joint disease secondary to laxity may cause pain/lameness in the older dog, with a reduced range of joint movement.

10. Well-muscled forequarters (weight shifted cranially).

11. Age predisposition

  1. Acute signs: <12 months of age.

  2. Chronic signs: older animals.

12. Breed/Species predisposition

  1. Large/giant breeds. Some breeds have a high incidence of disease, and breed eradication schemes are in place:

    1. German Shepherd dogs.

    2. Golden Retriever.

    3. Rottweiler.

How is Hip Dysplasia Diagnosed?

Normal hip

Hip dysplasia diagnosis is made by:-

  1. Client history,

  2. Clinical signs,

  3. Radiography (X-ray)

  4. Palpation of instability through various tests:-

    1. Barden test.

    2. Ortolani test, used in conjunction with Barden test.

There is no correlation between the radiographic appearance of hip joints and the degree of lameness or disability.

A number of control schemes are in existence because of the inherited nature of hip dysplasia (HD). The schemes are based on the examination and evaluation of radiographs (x-rays) of hip joints by specialists:-

  1. KESCAVA / East Africa Kennel Club Hip Dysplasia Scoring Scheme (Kenya) - The Kenya Small and Companion Animal Veterinary Association (KESCAVA) / East Africa Kennel Club (EAKC) Hip Dysplasia Scoring Scheme assess dogs' x-rays to look for abnormalities in hip joints. The veterinarian takes the X-rays to the KESCAVA Hip Scoreboard to be assessed by a panel of experts that analyses them and then issue a “score” which is returned to the client via the veterinarian. The results are also sent to the East Africa Kennel Club for recording on the dog’s registration.

  2. BVA / Kennel Club Hip Dysplasia Scoring Scheme (UK) - The British Veterinary Association (BVA) and The Kennel Club (KC) Hip Dysplasia Scheme assess dogs' x-rays to look for abnormalities in hip joints. A panel of experts provide a graded score for each x-ray. Veterinarians organise this for their clients and send the x-rays off to be scored and then relay the dog’s results back to the client.

  3. PennHIP® scheme for hip dysplasia (USA and Canada). - This is a scientific method for the early diagnosis of Canine Hip Dysplasia (CHD) based on joint laxity. It was developed in the 1980s by Dr. Gail Smith, a veterinary orthopedic surgeon and bio-engineer, and his colleagues from the University of Pennsylvania School of Veterinary Medicine. PennHIP® scheme refers to University of Pennsylvania Hip Improvement Program. It has been available for veterinarians and breeders since 1993.

  4. Hip dysplasia OFA certification scheme. - The Orthopedic Foundation for Animals (OFA) has developed a hip dysplasia scoring scheme that classifies the severity of disease in individuals. Identification of affected individuals allows for selective breeding.

How does Hip Dysplasia develop (Pathophysiology)?


Being a genetically mediated condition, laxity or instability of the hip joint develops early in life in predisposed breeds, influenced by environmental factors. The joint laxity is aided by increased joint fluid that encourages inflammatory joint disease (synovitis) causing pain and lameness initially. The joint capsule thickens, initially, that leads to joint stabilization. The hip then remodels progressively by the erosion of the borders of the hip socket (acetabulum), the eroded particles filling the hip socket, and new bone forming along the margins. The ligament (teres ligament) that anchors the head of the thigh bone (femur) into the hip socket (acetabulum) ends up overstretched and rupture causing further joint laxity leading to incomplete dislocation (subluxation) or complete dislocation (luxation).

An illustration anatomy of a hip joint with dysplasia, subluxation and dislocation of the femoral head in the joint .
An illustration anatomy of a hip joint with dysplasia, subluxation and dislocation of the femoral head in the joint .

There is delayed muscle development in early puppy-hood because of pain and disuse resulting in poor soft tissue support of the joint. The head and neck of the thigh bone (femur)become deformed by stress-induced reformation of the joint leading to flattened head of the femur and new bone production around its neck.

Once the puppy is mature, the skeleton is mature, the hip joint becomes stable and there is no luxation (dislocation), but the range of movement is restricted. The hip joint changes in breeds predictable of this condition progress slowly after maturity dependent upon weight of dog and how active the dog is. The deterioration of the joint progresses gradually with continued erosion of the joint cartilage, narrowing of the joint space as new bone formation continues. Puppies at the age of one year with advanced secondary remodeling of the joint at 1 year of age may not go on to develop clinical signs of lameness during adult life. In adults no correlation has been found between radiographic appearance of hip joints and degree of lameness/disability.

What is the Norberg angle in the canine hip joint?

The Norberg angle is measured as the angle between a line drawn between the centers of the femoral head and a second line from the center of the head to the cranial acetabular edge. As the femoral head subluxates, this angle will become more acute.
The Norberg angle is measured as the angle between a line drawn between the centers of the femoral head and a second line from the center of the head to the cranial acetabular edge. As the femoral head subluxates, this angle will become more acute.
Norberg's angle (diagrammatic representation). In a good hip this angle exceeds 105°. Image by Animal Health Trust
Norberg's angle (diagrammatic representation). In a good hip, this angle exceeds 105°. Image by Animal Health Trust

Norberg angle (NA) is a measurement of femoral head displacement from the acetabulum. Norberg angle is calculated by drawing a line connecting the centers of the femoral heads and one from the center of each femoral head to the craniolateral acetabular rim on the same side. Norberg angle ≥105 degrees is considered normal.

How is Hip Dysplasia treated?


The following are the various options of treating or managing canine hip dysplasia.

  1. Conservative management

    1. Young dogs:

      1. Control rate of growth.

      2. Control obesity by careful feeding.

      3. Avoid free running - frequent short walks on leash.

      4. Tactical use of non-steroidal anti-inflammatory drugs.

    2. Older dogs:

      1. Monitor and adjust body weight.

      2. Adjust exercise pattern.

      3. Non-steroidal anti-inflammatory drugs.

      4. Steroids as last resort.

  2. Hip replacement This is an option in mature dogs and a relatively expensive procedure, undertaken only by experienced surgeons in the procedure as complications associated with the surgery can be severe and careful immediate aftercare essential to reduce the risk of implant luxation or bone fracture.

An illustration x-ray of human pelvis, Healthy hip, arthritic hip joint and total hip replacement.

3. Salvage surgery As a last resort, the head of the thigh bone (femoral head), is excised (femoral head and neck ostectomy) with unremitting pain.

How is Hip Dysplasia prevented?

  1. Working dogs, e.g. guide dogs, police, Army, and other working dogs, should have their hips assessed through the various hip scoring schemes before commencement of training. Radiographs should be taken after the age of one year and scored under the chosen control scheme and advice given on breeding/working level, etc.

  2. Conservative treatment is unlikely to prevent onset of the condition in a predisposed dog but signs may be less severe.

  3. Animals that score worse than the breed average in a hip scoring scheme should be removed from breeding programs. Dogs with low scores are most desirable, as their offspring are less likely to suffer from the effects of hip dysplasia. It is probably too late to prevent hip dysplasia by the time you acquire a puppy so it is important to make some investigations before.



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