I broke my patella earlier this summer, and it was immobilized for several weeks. When I took the brace off for good I lost a tremendous amount of strength. Once I got range of motion back below are the exercises the physical therapist gave me. This may have nothing to do with your injury, but the muscles around my knee were very week, and it wan’t tracking totally normal at first.
wall squats hold for 10 seconds build up to 30sec.
single leg variation of a wall squat (shorter hold time)
step-ups
step-downs
walking lunges
foam stability pad balancing