My 16 Year Old Daughter Has Swelling Above Both Elbows

My 16 year old daughter has swelling above both elbows (triceps area). She does play volleyball, and they are in off season, but do a lot of strenuous workouts. It is hard for her to bend her elbows to eat, brush her hair, etc... She mentioned that it is even difficult to clutch her hands (hard to write, hold something etc..). What could cause this?