I am having pain in knees. I saw the doc and he said it may be tendinitis. He gave me nsaid but no improvement do far. Its been a year now. Pls advise?

Seek medical help. If you haven't seen an orthopedic physician i would recommend starting there first. If you have, then having an evaluation by a physical therapist would be your next step. They can determine what issues may be contributing to your pain and provide a treatment program to help you improve.
Physical therapy. You may benefit from physical therapy. You should consult your doctor again, and ask if physical therapy could alleviate your symptoms.
Get another opinion. Before you go any further, seek a 2nd opinion with a rheumatologist or orthopedist.