My Granddaughter Is 23 And Get Bruised And Swollen Knees.

My granddaughter is 23 and get bruised and swollen knees. The doctor said it was bursitis. They have tried to drain it and it was the most painful experience she has had. She has marfans so could that have something to do with this situation. It will be one leg and the next time the other leg.
She just seems to not be able to find out if maybe exercise, diet or what could help.
Any help you can give us would be so beneficial.