Fig. 2.

Corticosteroid injection: longitudinal scan of the flexor tendons of the fourth finger using a high frequency (17 Mhz) linear probe over the metacarpophalangeal joint. The 25 G needle is clearly displayed (empty white arrow) with its tip at the tendon sheath distal to the A1 pulley (full white arrow). The drug is injected into the proximal recess of the tendon sheath (empty arrowhead). The X and bar on the right are markers of focus in the US display (X is the center, and the bar is the range of focus). FPT = flexor profundus tendon; FST = flexor superficialis tendon; MCH = metacarpal head; PP = proximal phalange.