Have a look at the images below. Shoulder pain.

So- still think it's calcific tendinitis?


The patient suffered an anterior dislocation previously. See the defect on the inferior glenoid rim on the radiograph above? That's a bony Bankart.


And if you go up to the fragment shown above, it does look suspiciously like a piece from the glenoid defect. It's too well-circumscribed and well demarcated. Also, with such a large calcific fragment, shouldn't there be more swelling of the tendon?


So, knowing what you now know, it's likely the bone fragment from the bony Bankart displaced up into the supraspinatus tendon! Take home message: if it's too sharp, look again. Calcific tendinosis is fluffy.

A few interesting images demonstrating the power of diagnostic musculoskeletal ultrasound.

A subdeltoid bursal effusion. Notice the loss of contact at the proximal part of the probe? It's because we are rounding the lateral part of the shoulder. This is a reminder that subdeltoid effusions can move, and can be located very laterally rather than at the level of the tear. So, you need to go all around the shoulder to look for fluid.

This is biceps tendon is not really normal. While there's no anechoic fluid collection in the tendon sheath, there's echogenicity surrounding the tendon. This is what chronic tenosynovitis looks like- not to be dismissed as normal.

An important plane of scanning to detect tendon tears. In this case, you see a defect in the anterior aspect of the tendon (the ovoid biceps tendon is well demonstrated). There are punctate echogenicities indicative of debris within a subacromial bursal effusion that has filled the tear gap. You can see the cartilage of underlying humerus. 

Another view with the relevant structures highlighted:
Ovoid- transverse view of long head of biceps tendon
Lines- cartilage interface