Degenerative Joint Disease
Aging takes it toll on everyone, animals as well as humans. Among the hardest hit are the joints, especially the articular cartilage inside those joints, which normally provides a smooth, low-friction buffer between the bones. A variety of causes, including age, can cause this cartilage to break down or develop fissures, resulting in severe pain, inflammation, and lameness.
Although degenerative joint disease (and the resulting arthritis) is generally considered a problem of older canines, it's appearing in more and more younger large-breed dogs as well. Selective breeding has resulted in the altering of bone structure in several breeds, especially larger dogs such as German Shepherds, Great Danes and Mastiffs. In these animals, many are now born with a defect that prevents the development of normal cartilage, leading to permanent early lameness in the shoulders, knees, and ankles. [...]