More than 7 million Americans have an artificial knee or hip, according to a study presented at the American Academy of Orthopedic Surgeons 2014 annual meeting.

Conducted by researchers at the Mayo Clinic, the study found 4.7 million Americans, or 1.5 percent of the total population, have an artificial knee and 2.5 million Americans, or 0.8 percent, have an artificial hip.

These surgeries were especially common among people 50 or older, of whom 2.3 percent have an artificial hip and 4.6 percent have an artificial knee.

— Mac McLean