Which post-surgery exercises in Philadelphia are most effective for restoring mobility and preventing complications? ?

My sister had knee surgery last month in Philly, and the physical therapist gave her a few exercises, but I’m worried she might not be doing enough to prevent stiffness or other complications. For people who’ve helped someone recover, what exercises really made a difference in regaining mobility and avoiding setbacks at home? Any routines or tips that worked well would be super helpful.