If we can find out the cause of pain then it would be easy to treat it as well. Obviously lack of vitamins is not the problem, otherwise by this time pain would have decreased. A xray of the knee and some basic blood tests are required to rule out common causes of pain. At your age the most common cause of pain arising from the knee is a torn meniscus. However, torn menisci can be identified only in an MRI. Visit an ortho surgeon who can examine the knee and order the necessary tests. He may also prescribe you meds to bring your pain under control.