Nina Dobrev is recovering from knee surgery with physical therapy and a CPM machine. Here's how the machine is supposed to help heal—and why it's controversial.

Dobrev underwent surgery on her knee and said treatment involved a CPM Machine — short for continuous passive motion — which is a motorized device that “gently bends a joint back and forth ...

According to Verywell Health, a CPM (or a continuous passive motion machine) is a "motorized device used in physical therapy that gently bends a joint back and forth to aid with recovery following ...

A CPM Machine — short for continuous passive motion — is a motorized device that “gently bends a joint back and forth to aid with recovery following a joint injury or surgery,” Verywell ...

A CPM machine is a “continuous passive motion” device that helps move a joint after an injury. “Thank you to everyone who has been sending kind messages, thoughts, prayers, and good vibes ...

Plus it is eight hours a day in a CPM machine for the first six weeks," says Erica. "Puts you down for a little bit, for sure. It's about a year recovery." Erica had her left knee done a year ago.