Pain on inside of right knee under kneecap for past year?

Kneecap: Get it checked out by an orthopedist. There are various reasons for possible pain at your age. It may be maltracking of the kneecap which can be treated with therapy. Other less likely problems are inflammation or cartilage wear.

Synovitis: In a 16 year old male, sometimes the knee can get inflamed and stay inflamed for a while. Often times people will have very tight hamstrings. This makes the quad muscle over work and push the knee cap into the femur bone causing pain.