I do squats and seated knee extensions and leg press which are generally pain free. I also do side and front step ups. I may have overextended myself and had a setback. I have had around 3 setbacks in 2 months of doing rehab during which the therapist has progressively adjusted the exercise program. Sometimes this happens when I stand up too quickly from a low bench at the gym. I recover with rest and sometimes some ibuprofen or Celebrex, especially if there is swelling.