Definition of Hip Dysplasia
Hip dysplasia is a common, painful canine disorder that involves abnormal development and/or degeneration of one or both hip joints. The hips are ball-and-socket joints where the head of each femur (the long thigh bone) joins with a concave socket of the pelvic bone called the acetabulum. Dysplasia means abnormal development of tissues, bones, organs or other structures. The hip joints of dogs with hip dysplasia have a genetic predisposition to partially dislocate, or subluxate, which means that the head of the femur is too loose, causing abnormal mechanical forces across the hips, irregularly shaped bones, damaged cartilage, microscopic bone fractures and, in severe cases, degenerative joint disease. 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 hip laxity. In older dogs, hip dysplasia typically comes from progressive degeneration and deterioration of bone and cartilage in the hip joint.