Doctors performed 299,000 total knee replacements in 2000, according to the American Academy of Orthopedic Surgeons. A 1998 study in the British edition of the Journal of Bone and Joint Surgery found that after 10 years, 90% of these procedures are successful. When only a single knee compartment is affected, doctors may perform a unicompartmental knee replacement. Recuperation can take three to six months. About 30,000 are done annually.
Knee fusion: Also called arthrodesis, this rarely performed operation is sometimes recommended when a knee replacement may fail. It fuses the femur bone to the tibial bone, resulting in a completely stiff knee.
Discosupplementation: A relatively new therapy, involving injections of lubricant to replace knee fluid that has become less slippery because of arthritis. Although the injected hyaluronic acid eventually breaks down, some patients report years of relief, Moseley said.
Unispacer: The most recently developed knee procedure, it involves making a single incision and sliding a metal disk between the bones of the leg. Although FDA-approved, the procedure has been performed 900 times to date by the 350 orthopedic surgeons who have undergone training by the manufacturer. Said Dorr: "It may be the next easy solution for arthritis in the knee, like arthroscopy was, but there's no good data yet that say it's going to work."