usually when there is a fracture, they immobilize the joint above and if necessary, the joint below as well. This prevents you from moving the injured limb as many muscles cross over multiple joints. If you move your elbow, some muscles that attach by the wrist as well will move and cause the bones at the fracture site to shift. Then the fracture will not heal well. ( before I became a stay at home mom 5 yrs ago, I was a PT. Well, still am but not working)
Jan