Follow-up care for shoulder bursitis often includes physical therapy. Treatments, such as heat, ultrasound, electrical stimulation, ice and compression, are used to decrease pain and muscle tightness. Heat treatments are not applied until a few days after a cortisone shot to avoid increased risk of a flare reaction.mmediate Care. Cortisone shots can cause a flare reaction in the first 24 to 48 hours. This can be caused by the body responding to the needle injury or from small crystals that form in the injected tissue.