This in a injury to the tendons that start on the outside of the elbow and travel down to extend the wrist and fingers. This can be a very frustrating injury to treat. Its not unusual to try one or two cortisone injections for lateral epicondylits (tennis elbow). However, it is not entirely clear why the injections are effective since this is not really caused by inflammation, but rather by microtears within the tendon. The MRI finding is not unusual, and is consistent with lateral epicondylitis.
I have had very good success with platelet rich plasma injections (PRP) for this problem. Platelets contain growth factors. In this therapy, your own blood is drawn, and spun to obtain a high concentration of platelets. The concentrated platelets are injected into your tendon to deliver the concentrated growth factors and induce a healing response. This treatment ihas had about 80% success rate.
I see about 200 patients with tennis elbow a year, and find surgery necessary on less than 5%.