Tennis elbow is a repetitive stress injury that results from improper stroke technique and occurs in the lateral epicondyle for backhands and the medial epicondyle for the serve and forehand. All too often the joint is treated with a cortisone injection and physical therapy and the person is told to return to playing tennis when the pain is resolved. Unless proper stroke production is taught there's little reason to expect that this injury will recur.
A study published in JAMA in February of 2013 measured the effectiveness of cortisone injections and physical therapy over one year. They found that a single cortisone injection was associated with poorer outcomes after one year and higher recurrence rates than a placebo injection. Adding 8 weeks of physical therapy did not significantly improve the long term outcome. We know that cortisone has a powerful anti-inflammatory effect which is very effective in the short term, but we also know that it slows down the healing process substantially!
We use infrared light therapy because it just as effective as an anti-inflammatory agent and it also speeds up healing by about 50% according to NASA studies.