Osteoarthritis Knee Pain Treatment & Prevention: Knee osteoarthritis involves degradation of the knee joint, eventually leading to pain and loss of function. More than 10 million Americans are affected by knee osteoarthritis. The condition is seen most often in people age 45 and over, as cartilage wears away through wear and tear. Most common complaints are joint swelling (inflammation), stiffness, and pain. Knee osteoarthritis can be diagnosed using X rays to indicate boney cysts, narrowing joint space, and sclerosing of the bone.