Osteoarthritis is characterized by the breakdown of the articular cartilage, the firm whitish-colored rubbery protein material covering the ends of bones. It acts as a cushion and bearing surface between the bones, allowing them to glide smoothly over each other with almost zero friction. Osteoarthritis commonly affects large weight-bearing joints such as the hip and knee, but may affect any joint.
The exact cause of knee osteoarthritis is unknown. Some contributing factors include: previous injury, aging, misalignment, genetics, and obesity. The number one symptom of osteoarthritis of the knee is pain. The causes of pain in osteoarthritis include: irritation and pressure on the nerve endings in the bones, inflammation of the joint lining (synovitis), muscle tension and fatigue. The pain may progress from mild soreness and aching with movement to severe pain even during rest. The second symptom is loss of easy movement. As the lining cartilage wears away, the joints no longer glide smoothly.