Hardened bump/cartilage and side knee pain when bending

Patient: Hi,There is some kind of hardened bump/cartilage that appeared on top portion of knee side(facing right leg) of my left knee.When I bend my leg I can feel it grinding and it can be a painful to bend full when it appears, but after couple of hours it is only uncomfortable to bend it fully. This thing used to appear previously too, once or so a year, but usually would go away after couple of days. This time I have it for over a week and it has not disappeared. I do not believe there was any trauma to the knee as it appeared after long sitting when i stood up from a chair.Any idea what it could be?

Symptoms: Uncomfortable side knee pain when bending

Images:
Hardened bump/cartilage and...-1 Hardened bump/cartilage and...-1

Doctor: