thanks for your question. well kindly look for any of the following things 1. if child ever had fever prior swelling 2. any diarrohea, rash few days back or recently any abdominal pain. 3. any other joint with similar complaints simultaneous or sequential. 4. any eyesight problem... 5. any breathing problems or palpitations also we need some blood tests like blood count, esr , crp and some antibodies like ana , anti jo anti la. simple bursitis will have pain throughout a day. so most likely other disorders are to be ruled out. kindly show to a rheumatologist. mean while you can start simple ibugesic.