Bieber's official diagnosis which sent him to the injured list is right elbow inflammation, Mandy Bell of MLB.com reports.
Bieber was initially reported to be dealing with a forearm injury, but the issue is evidently with his elbow. The fact that he's merely been diagnosed with inflammation rather than a strain is an encouraging sign, though there's still the possibility of a more serious injury, as he doesn't yet have a clear timeline for his return.