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We now know that a cortisone injection interferes with the body's natural healing process, which works like this: When tissues are overused, overstretched or torn, the cells of those tissues release factors that recruit blood vessels, stem cells and healing factors. With that in rush of fluid, the tissue temporarily swells. Over time, with the laying down of new collagen -- the protein that makes up most of our body -- the injured tissue heals. Some tissues heal normally; others with scar tissue, over time, often can remodel into normal tissue.