We worry about juvenile arthritis if there is daily persistent joint swelling for at least 6 weeks.  If the joint swelling is transient, and goes away within 6 weeks, than that would not be consistent with a chronic problem.  Transient joint swelling could be caused by a reaction to an infection such as a virus and the joint issues go away without treatment.  In an older child (like age 8), transient joint swelling could come after a Strep throat (which is rheumatic fever).  Another possibility is if your child is very flexible, that can cause joint pain and mild swelling after activity.  The treatment for that is physical therapy.  Some kids with flexible joints also have nose bleeds, easy bruising,  and this is associated with rare conditions like Ehlers-Danlos and Marfans.  The 2 most likely considerations for your daughter would be joint hypermobility or a post-viral arthritis that will go away, but I would have you discuss these issues with your doctor.