Advances in all aspects of joint replacement have dramatically changed the prognosis for patients undergoing joint-replacement procedures. The latest joints now last longer-potentially 15-20 years or longer-and allow for a higher level of activity than previous generations of artificial joints. For nearly 40 years, artificial joints were primarily made of polyethylene, a type of hardened plastic. "But the material had drawbacks that limited its longevity," says Wael Barsoum, MD, vice chairman of orthopaedic surgery at Cleveland Clinic. "When the material wore down, it released particles that caused inflammation. Doctors realized that if they could reduce the amount of particle debris, they could offer patients a joint with a longer lifespan."