What causes osteoarthritis of the knee?
Osteoarthritis of the knee usually occurs in knees that have experienced trauma, infection, or injury. A smooth, slippery, fibrous connective tissue, called articular cartilage, acts as a protective cushion between bones. Arthritis develops as the cartilage begins to deteriorate or is lost. As the articular cartilage is lost, the joint space between the bones narrows. This is an early symptom of osteoarthritis of the knee and is easily seen on X-rays.
“Osteoarthritis (OA) of the knee is one of the five leading causes of disability among elderly men and women. The risk for disability from osteoarthritis of the knee is as great as that from cardiovascular disease.”
As the disease progresses, the cartilage thins, becoming grooved and fragmented. The surrounding bones react by becoming thicker. They start to grow outward and form spurs. The synovium (a membrane that produces a thick fluid that helps nourish the cartilage and keep it slippery) becomes inflamed and thickened. It may produce extra fluid, often known as “water on the knee,” that causes additional swelling.
Over a period of years, the joint slowly changes. In severe cases, when the articular cartilage is gone, the thickened bone ends rub against each other and wear away. This results in a deformity of the joint. Normal activity becomes painful and difficult.