Depends alot on what kind of issues you have.
Had knee issues from sports from when I was around 14 until I started squatting when I was 20.
Squats seems to have been the exercise that actually fixed my knee and has always been that movement that feels most natural and least aggravating.
Squats is for example the nr.1 prio exercise I was told do to use to rehab the patellar tendinitis I've had since january.
Otherwise these are typically not very stressing;
Legcurl, Bulgarian splitsquat, RDL/SDL.