Strange noises from the knee?

Any suggestions? My knee has started to click on climbing and going down stairs. It also “graunches” and feels like something is rubbing on something. If you place a hand on it you can feel the vibrations like if moving a handful of small pebbles around in your hand.

No “pain” as yet but a definite “warmness” from the joint and mild discomfort.

I jog about a mile twice a week in proper running shoes but the problem has only surfaced in the last week after having been laid up for 7 weeks straight with an injured back so it is well and truly rested.

Cheers