Re: sharp pain just under patella when extending knee
I have a similar problem with my left knee except there's more of a clunking sound in the knee joint when I extend the leg all the way and experience the sharp pain at a greater angle than that. I've gotten the diagnosis of patellafemoral pain and more recently plica syndrome/ hoffa's fat pad. What you're describing sounds like patellafemoral but I'd have it checked out. The doctors that I've talked to have said that often males with tight hamstrings have a tight lateral retinaculum which causes the patella to track to the outside which throws off the mechanics of the entire knee joint. Most likely if you see an orthopedist the first thing they'll do is prescribe physical therapy, that is if they don't order the MRI first.