I had arthroscopic surgery 6 weeks ago. My knee locks up and builds pressure and sometime cracks very deeply. Thoughts?

More info needed. Hard to advise unless i know exactly what was done as well as findings at the time of surgery.
See your orthopod -- Who performed the surgery, about it, as he would be in the best position to tell you what he saw and did. U had a shattered patella last year, this could all be due to that. Check with your surgeon. Good luck.