Hip Dysplasia - An overview and Key Signs To Be Aware Of

Hip dysplasia occurs in many species (including humans and cats) but is mainly a concern in dogs. It can occur in any breed or size of the dog but is more common and tends to be a bigger issue in larger breeds.

The hip is the ball and socket joint that connects the hind limb to the pelvis. The femur is the thigh bone. The ball is called the femoral head, and the socket in the pelvis is the acetabulum.

The ball and socket grow in concert with one another in the normal hip joint. The ball sits deeply in the socket and rotates within. The ball and socket are held together by a ligament (a band of tough tissue between the bones), a joint capsule (which also contains joint or synovial fluid), and muscles that connect the pelvis to the femur. Articular cartilage (joint) lines the ball and socket.

In a hip with dysplasia (dysplasia meaning abnormal growth and development), the connection between the ball and socket becomes looser than what is considered normal. This results in abnormal movement of the ball in and out of the socket in addition to the regular rotation, and the shape and depth of the socket or the shape of the femoral head may also be altered.

A scale is used to rate a hip’s condition, with “more normal” on one end of the spectrum and “more dysplastic” on the other. The higher the rating is on the dysplastic side, the more likely the dog will show abnormal movement as they walk or run.

Healthy joint cartilage and proper lubrication by joint fluids result in a nearly frictionless and smooth motion. Abnormal hip movement affects hip function, tiring the muscles surrounding the hip as the dog moves or engages in activity. This abnormal motion eventually wears down the joint cartilage and can result in permanent damage with loss of smooth function.

Damaged joint cartilage does not repair well, and further changes to cartilage and bone occur as the process continues. These changes and the resultant bone-on-bone rubbing from the loss of cartilage can cause pain. This process of cartilage damage, loss, and changes to the joint capsule and bones is termed osteoarthritis (“OA”) or degenerative joint disease (“DJD”). 

Signs of hip dysplasia may be observed in puppies before one year of age. Most of these signs will be those of mechanical lameness, although some may have early symptoms of arthritis as well.

In some dogs, signs of mechanical lameness may seem to disappear at around one year of age until about the ages of two to four years, when osteoarthritis progresses and symptoms recur.

However, many dogs with hip dysplasia never have recognizable signs or only display such signs when they are older.

Puppies with dysplasia may “bunny hop” with the two hind limbs together when running or climbing stairs.

Before OA sets in, young dogs might not be in obvious pain except for some muscle soreness. The signs often do not respond much to analgesics (pain medications) or anti-inflammatory medications.

An owner might notice poor muscle development in the dog’s hind limbs or notice the hip bones seem more pronounced. This is due to poor muscle mass around the point of the hips.

Sometimes, an obvious “pop” from the hip area can be heard or felt as the dog moves because the ball is moving inappropriately in and out of the socket.

       

Even in “normal” joints, arthritis can be a part of aging, but if a dog has dysplasia, arthritis can develop much sooner than it might in a dog without the condition. The signs of pain and limping or lameness are more likely when arthritis is present.

Arthritis pain is more responsive to anti-inflammatory and pain medications than mechanical lameness alone. Your dog’s lifestyle can affect the degree of pain. Working dogs may exhibit more pain than less active house pets. 

Thigh muscle atrophy (loss of muscle mass) may be noticed as the dog bears less weight on the affected limb.

Article written by 

Dr. Willem Vergeer