Sounds similar to myself. I can go a week with tight clicking knee state. And other times a week with much looser knee. See no pattern determining this. I am 65 and still play tennis. I do not dare run. But can read well enough to walk to most shots. Yesterday knee very tight and clicky and painful. Ended up rallying with a man in his 30s with powerful and consistent technique. Was so engrossed in hitting the ball that I found the knee state receded. Rotated - I think off the ground - to get good speed through the ball. And was matching this man's pace even if not the consistency. It was supremely energising and exciting. And the knee at the end seemed much in the same state as at the start but less so. A lot of the psychology of pain is about body image - if we sense all is fine the pain level reduces. If we catastrophise, it can increase. Hope this rambling essay makes some sense.