Knee pain is actually a fairly common complaint. There are many causes of knee pain, some of which are minor and some of which are significant. I would recommend that you discuss this with your primary care physician
. A simple evaluation can prevent missing a serious cause of knee pain.
The knee is a fairly complicated joint -- a requirement given then need to be fairly flexible as well as withstand the fully body weight. The knee has many components -- the bones, joints, meniscus (the shock absorbers) and muscles/ligaments/tendons that support the knee. Any of these can fail and thereby cause pain.
The most common cause of knee pain in young people like yourself is called patellofemoral syndrome. This is a problem with them muscle/tendons and how they hold the knee cap in place. This can be improved with stabilizing the knee and often physical therapy. Bone problems can also occur -- simple wear and tear on the bones is known as osteoarthritis which can often be painful. Damage to the meniscus or ligaments can also cause pain -- although often caused be a specific injury
Talk to your doctor
. This is likely a small muscle problem that a brace and therapy can help -- but ensuring there is not a more serious problem would be helpful. Good luck!