The Hip Joint

The hip joint is a ball and socket joint which comprises the head of the femur (thigh bone) and the acetabulum (socket) of the pelvis. In a normal hip joint the femoral head sits deeply within the acetabulum to provide rotational ability to the joint. The joint is held together by a ligament (tough band of tissue between the bones), joint capsule, and the surrounding muscles. Articular cartilage lines the inside of the joint providing shock absorption and smooth easy movement between bones. 

The Dysplastic Hip

In hip dysplasia the ball and socket connection is loose, thereby altering the mechanics of the joint. The shape and size of the femoral head (ball) and acetabulum (socket) may also be altered. These changes can range from very mild to severe. 

Why do the mechanics matter?

When the mechanics of a joint are altered, all the involved structures are compromised. Muscles get sore from compensating, cartilage accumulates abnormal wear and tear, and the joint capsule is under constant altered pressure/stretch (there are pain receptors in there – think over extending your wrist.) Over time, damage to the cartilage and joint capsule together are termed degenerative joint disease. 

What causes it?

Hip dysplasia is caused by a combination of complicated factors including genetics and environment. Previously considered entirely inherited, hip dysplasia is classified as a developmental disorder as dogs with “normal hips” can over time develop the condition. A combination of factors including growth rate, obesity, hormones, and diet make up the primary environmental influences however the primary cause is genetics. Typically 95% of dogs will have detectable signs by the time they are 2 years old, although many do not show clinical signs until later in life. 

What does Hip Dysplasia look like?

In younger dogs symptoms typically do not overtly look like pain. They can include:

• Problems jumping in cars, rising from a laying position, or stair navigation
• Disinterest playing with other dogs or seeming to “tire” easily
• Needing to lay down or sit on walks
• Bunny hopping while running (using both hind limbs together)
• Excessive side to side sway of the hips during walking

In older dogs symptoms include the above but also encompass more traditional arthritis/pain signs. They can include:

• Vocalizing with limb handling
• Limping
• Reluctance to move
• Hind limb muscle atrophy
• Behavior changes (lower tolerance of human/animal contact)

How do we diagnose it?

Pelvic radiographs are the gold standard for diagnosing hip dysplasia. A variety of specialized orthopedic tests and gait analysis can be highly suggestive however. Hip dysplasia can be diagnosed in any breed, sex, or age animal. (people and cats too!)

Isn’t it just a YOUNG dog thing?

Screening for hip dysplasia traditionally has been in young, oftentimes breeding animals. Therefore, it was more commonly found in young animals. However hip dysplasia can be found in any age animal, in fact many cases of mild hip dysplasia are not found until adult years as it takes time to build up enough damage to cause signs we can see in our dogs.

How do we treat Hip Dysplasia?

The first step is getting a diagnosis. Depending on how severe hip dysplasia is, a surgical consult may be recommended by your regular vet or rehab provider. A large percentage of cases are mild/moderate and respond to appropriate weight management, supplements, medications, but most importantly preventing hind limb weakness with canine rehabilitation. Promoting appropriate gait motion and hind limb strength can help stabilize the abnormal movement in the hip joint. This is done with targeted canine rehabilitation exercises, and management of compensatory pain/discomfort.

Bottom Line

Hip dysplasia is a lifelong diagnosis, however most dogs with hip dysplasia can live normal lives with appropriate multidisciplinary management.