Any condition affecting the knee that causes damage to the normally smooth lining cartilage of the knee may eventually end up with the same end result. The protective cartilage lining the joint becomes worn away, producing increasing damage to the bone surfaces inside the joint. This may cause pain, swelling and stiffness, as the exposed bone ends grind painfully against each other.
Osteoarthritis resulting from "wear and tear" is the most common reason individuals need to undergo knee replacement surgery. This condition may be due to an old injury or infection to the knee joint, but mostly there is no obvious cause as to why this happens. The major problem in osteoarthritis of the knee joint is that the smooth cartilage lining the inside of the joint wears away. This results in a narrowing of the joint space with the development of cysts and erosions in the bone ends. As a result, bone comes directly in contact with bone, which will be painful. Bone spurs (small bone growths) form around the joint. All of these changes ultimately lead to increasing pain and stiffness of the joint.
Rheumatoid arthritis, an inflammation of the tissue surrounding the joints, can cause deterioration of cartilage and other parts of the joint and result in the need for knee joint replacement. It is one of the inflammatory types of arthritis that may affect other areas of the body such as skin, kidneys and spleen. Rheumatoid arthritiscan also affect other joints including hands, feet, elbows, hips etc.
Post-traumatic arthritis, a type of arthritis that can arise following an injury to the joint cartilage or through damage to the ligaments leading to an unstable knee. Generally speaking, any abnormalities causing excessive wear within the joint (from fractures of the knee, torn cartilage, and torn ligaments) can lead to degeneration long after the original injury and ultimately result in the need for a knee replacement.
Avascular necrosis results from an inadequate supply of blood to the bone end inside the joint. As a result articular cartilage wears away.
Malalignment of the knee joint - knock-knees or bowlegs - results from an excessive angle where the upper and lower leg bones meet at the knee joint. The result is abnormally high stress on either the outer half or inner half of the joint.