How uncommon is deltoid tendinitis?

Today I did a Google search for my current ailment, deltoid tendinitis, and not finding that much, came away with the impression that it is somewhat uncommon. Wikianswers.com says so directly, and my physical therapist's reaction seemed to suggest it. There's one question for my physical therapist! The other is if my tendinitis has reached a chronic stage, which would mean that it might take 6 weeks to heal.