My 16 year old daughter, who is a very athletic individual (lifeguard, hiker, bike rider, swimmer), has recently experiences swollen painful knees. At times, in the morning especially, she finds it difficult to walk and almost impossible to bend at the knee. It is obviously a tissue swelling that causes this, but what is causing the tissue to swell? Is it a form of Bursitis, perhaps, or are there other issues that have these common symptoms. It stays for a few day/weeks then subsides, then returns. Should I take her in for an MRI or try some at home remedies/recovery habits to curb it?