In its sixth year, Operation Walk USA, an independent medical humanitarian organization, is taking place in Chicago, Illinois.
Here are seven things to know:
1. The organization offers free hip or knee replacement surgeries to U.S. patients that do not qualify for government assistant programs and can't afford the surgery on their own.
2. This year, 80 patients will receive free joint replacements from 55 volunteer orthopedic surgeons at 40 hospitals from Nov. 30 to Dec. 5.
3. The program takes place annually in early December to allow for not only greater hospital, surgeon and medical staff participation, but also as a holiday gift to the patients it treats.
4. It provides numerous treatments, including surgery, hospitalization and pre- and postoperative care at no cost to participating patients.
5. The most common cause of disability in the United States is arthritis, affecting approximately 46 million Americans, or more than 21 percent of the adult population.
6. Operation Walk USA first began in 2010 following the success of Operation Walk, an international volunteer medical service organization that provides treatment for patients with arthritis and joint conditions in developing countries.
7. DePuy Synthes, Smith & Nephew, Stryker, Total Joint Orthopedics and Zimmer Biomet are some of the device manufacturers donating their hip and knee implants for the 2015 Walk.