23 y/o w/ chronic swelling of the knee & stiffness after marathon training. clean mri and blood work except 1:320 ana titer. no suspected ra. ideas?

Joint fluid analysis: Although it's possible that this is related to your marathon training you need to have a joint fluid analysis to see if it's inflammatory or not inflammatory, if it's infection or not infection and to see if there are crystals or no crystals. You need a evaluation to make certain what is going on inside the joint. An MRI is not sufficient.