Causes of Canine Hip Dysplasia
Genetics almost certainly influence the occurrence of hip dysplasia in dogs. However, the exact contribution of genetics to this disease is not well understood. Some combination of hereditary, nutritional and environmental factors leads to looseness, or laxity, of one or both hip joints in affected animals, which makes the joints unstable and accelerates the progressive degeneration of bone and cartilage. Puppies that are predisposed to developing hip dysplasia can be born with hips that look normal but really aren’t and eventually begin to deteriorate. Conformational hip abnormalities in young dogs typically can be seen on X-rays (radiographs) within the first few weeks of life. By 6 months or so, affected youngsters usually start showing gait abnormalities and rear end lameness. Mature dogs that develop hip dysplasia later in life tend not to have structural deformities of their pelvic and thigh bone junctions from birth. Instead, their hip joints degenerate progressively as they age – which essentially is degenerative joint disease (DJD), or osteoarthritis, of the hip. Obesity can accelerate the onset of hip dysplasia, as can trauma.
Preventing Hip Dysplasia
According to current research, the best way to prevent hip dysplasia is to screen dogs and remove them from the breeding population if they have radiographic evidence of dysplastic hips. This is still somewhat controversial even among reputable breeders, because dogs with excellent hips can produce dysplastic puppies, and dysplastic parents can produce puppies with excellent hips. However, since there probably is a genetic component to this condition, most cautious breeders will not knowingly use dysplastic dogs in their breeding programs, nor will they repeat breedings of a male and a female that previously produced dysplastic offspring. Another preventative measure is to avoid feeding young, rapidly growing large and giant breed puppies a diet that is extremely high in fat, calories or protein. Dietary overstimulation has been shown to contribute to growth-related bone, joint and cartilage abnormalities in rapidly growing large youngsters, including osteochondrosis dissecans (OCD), hypertrophic osteodystrophy (HOD) and hip dysplasia. Dogs of all ages and any breed or mixed breed should have their weight managed to prevent obesity, which can put excessive stress and abnormal pressure on the hips and on other joints. Young dogs should not be exercised heavily, especially not during the first year of their lives. They should be prevented from leaping into the air (such as chasing a Frisbee) and landing full force on their hind legs. They should not be allowed to stand up on their rear legs and jump on people or peer over a fence. Puppies should be kept from jumping off furniture or out of the back of pick-up trucks or tall SUVs.
In young dogs, hip dysplasia usually is caused by conformational abnormalities that cause a “poor fit” between the head of the femur and the pelvic acetabulum, which in turn causes laxity of the hip joint. In older dogs, hip dysplasia typically is related to progressive degeneration and deterioration of bone and cartilage in the hip joint over time.