(English captions by Andrea Matsumoto from the University of Michigan)

To perform O'Brien's Test point the thumb
down and flex shoulder to 90 degrees.

Adduct the arm across midline, provide resistance
against further shoulder flexion and evaluate

for pain.

Repeat with the thumb pointing up and again
evaluate for pain.

If pain was present with the thumb down but
relieved with the thumb up, it is considered

a positive test, suspicious for a labral tear.