Knee stiffness

I am noticing I am having more stiffness and tenderness near or in my knee caps. I am wondering what some of the issues may be that might be contributing to the problem. I have had a bike fit. And this knee thing has been going on for a while, I have not increased training volume, so things are mostly constant.

I know there are a lot of pieces, so I’m not sure where to start troubleshooting. Maybe a video about what to check in order to rule out causes for the individual. Like a self-help checklist. Thanks Grant