The good news is he does not have any ligament involvement. The big question is how can they get the impingement cleared up so he doesn't miss an extended period of time or need surgery. The arthritis portion isn't serious because a lot of ballplayers experience arthritis-like conditions in various joints in the body.
Because impingement syndrome is not that common in MLB pitchers, it's hard to make a projection on how long he'll be out. Most likely, it is a posterior (back of the elbow) impingement, the result of overuse of the elbow joint over time.
The fact the swelling responded quickly to the oral medication he took last week is a positive. The fact the swelling returned after a throwing session on Saturday isn't.
Unless the case is moderate to severe, which his doesn't appear to be, anti-inflammatory medication, along with therapy to build up strength and increase the range of motion of the elbow, represents the most likely course of action.
Based on the available information, I project he will miss three to five weeks.
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The Baseball Injury Report is published by Rick Wilton, fantasy baseball's most experienced injury analyst. Rick, with background in radiology, pharmacology and physical therapy, has been a contributor to STATS Inc., Sports Weekly Hot Sheet, and BaseballHQ.com.