The primary site of involvement is the articular cartilage. Fissuring, pitting and erosion are the gross findings. The water content of the articular cartilage is significantly increased. The proteoglycan content of the cartilage is decreased. The ratio of chondroitin 4-sulfate to keratan sulfate is increased.
Marginal osteophytes form in response to the primary loss of articular cartilage.
This may represent an inefficient form of the cartilage trying to repair itself. Articular cartilage is mostly type II collagen. With surgical attempts to debride and stimulate formation of new cartilage, the new fibrocartilage is formed which consists of type I collagen. Lab tests are generally normal. There is usually no elevation of the sed rate.