A recent study from Denmark found neither steroid nor platelet injections improved pain and functioning among people with tennis elbow any better than placebo shots over a period of three months. A follow-up study by researchers from the University of Queensland in Australia randomly assigned 165 adults with tennis elbow to one of four treatment groups: cortisone shots vs. placebo shots and physical therapy vs. no physical therapy. After one year, there was no difference in people's improvement in pain or functioning based on whether they'd had the eight sessions of prescribed therapy, and a slightly greater percentage of those receiving placebo shots showed improvement. "This evidence does not support the clinical practice of using corticosteroid injection to facilitate active rehabilitation," the study team wrote.
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http://www.reuters.com/article/2013/02/05/us-steroid-tennis-elbow-idUSBRE91417X20130205