They're part of a nationwide event called "Operation Walk." Several people at Keck Medical Center of USC are seeing their lives change as a result. The center donated time, equipment and space, and dozens of nurses, doctors and volunteers their time to patients who couldn't walk with debilitating pain from worn-out hips and knees, and couldn't afford joint-replacement surgery.
Danny Gonzalez, 55, has been trying to make ends meet as a cab driver since his tile and masonry business has taken an economic hit. But wear and tear on his hips put him in a wheelchair.
"My hip was actually shattered. I only had less than an eighth of my hip ball left," said Gonzalez. "It was shattered, completely gone."
He gained weight, ballooning up to 409 pounds. He needed a hip replacement, but his insurance denied him due to his failing health.
"A lot of doctors just looked at him and said 'No, we don't want to help you,'" said Jessica Santaniello, Gonzalez's daughter.
In desperation, Gonzalez's relatives found Dr. Lawrence Dorr, an Operation Walk doctor. The organization and the doctor agreed to take his case.
Dr. Dorr and 150 other volunteer surgeons in more than 50 medical centers across the country performed free hip and knee replacements on about 200 patients, including four at Keck Hospital at USC.
Last year, Operation Walk volunteers replaced Gonzalez's left hip. Friday morning, using the latest in joint-replacement technology, USC doctors replaced his right hip.
"To be able to get people their life back in their daily activities, getting out of bed, putting on their shoes and socks without pain, it's really rewarding," said Dr. Daniel Oakes, Keck Hospital.
An hour after surgery Friday, nurses got Gonzalez up and nearly running.
"I was in a wheelchair when they first brought me in," said Gonzalez. "And now I'm swimming, walking, got a smile on my face."
Friday, three other patients also received free hips and knees and are all recovering well.
Operation Walk USA performs these free surgeries around this time every year.