I Am An Active 58 Yr Old Male Without Health

I am an active 58 yr old male without health issues and recently developed a very frequent clicking noise n my right knee as I step. It is loud enough others n room can hear it. I do not feel the click but the knee appears a little swollen and is uncomfortable to bend much. I will b calling my doc for an apt n morning. I am beginning a weight loss diet although I'm not but approx 25 lbs overweight. Any advice besides an anti-inflammatory. What would b your diagnosis? Thx