It involves the naturally occurring lubricant which forms over the surface of metal-on-metal parts once they are implanted in a patient.
Doctors at Northwestern and Rush University Medical Center discovered the lubricant is graphite-based and not comprised of proteins from within the patient's body.
The doctors say the lubricating layer acts like motor oil in a combustion engine.
Although further study is needed to pinpoint the origin of the lubricating graphite, doctors are hopeful the discovery will lead to longer life spans for prosthetic hips, ideally lasting the patient's lifetime.
"Knowing that this type of graphitic carbon can form gives us a target, if u will, to understanding how we can improve the performance of metal on metal bearings, take advantage of the finding to come up with ways to make that graphitic surface more adherent, hopefully leading to uniformly low wear over time," said Dr. Joshua J. Jacobs, Rush University Medical Center.
Each year, more than 450,000 Americans undergo hip replacement.
Northwestern and Rush doctors worked with German researchers on the study, which will be published Friday in the journal Science.