During hip replacement, a surgeon removes the damaged sections of your hip joint and replaces them with parts usually constructed of metal and very hard plastic. This artificial joint (prosthesis) helps reduce pain and improve function.Also called total hip arthroplasty, hip replacement surgery may be an option for you if your hip pain interferes with daily activities and more-conservative treatments haven't helped. Osteo-arthritis damage is the most common reason to need hip replacement, followed by rheumatoid arthritis and hip fracture.