Review Question - QID 7664

Figures 76a and 76b are the sagittal T1-weighted MRI scans of an active 27-year-old man who has had left dominant extremity shoulder pain and weakness for the past 5 months. He denies any history of a precipitating event but recalls that the pain began around the time he started lifting weights after a year off from lifting. Examination reveals full range of active and passive motion, negative Hawkins and Neer impingement signs, 5/5 abduction strength, 5/5 external rotation strength with arm adducted at his side, and a negative belly press, Gerber lift-off, and O'Brien's test. He does have weakness with resisted external rotation with the arm abducted to 90 degrees. Radiographs are unremarkable. An MRI arthrogram shows no rotator cuff tear or labral tears. What is the most likely diagnosis?