I've had cortisone injection which took about 6 weeks to clear the triggering, and lasted about 4 years.I had it done in hospital, and it hurt like help having it done.
When it came back, I put off seeing the doctor, knowing what I was in for. Eventually, I got it done by my g.p. and it hurt a lot less, he used a smaller needle, I think, but it is back again after probably 2 years.
Also, I was given a slightly different explanation of my condition to the one above, that the growth was on the tendon rather than the pulley, and it is this that snags in the pulley. Same effect but not exactly how NJ described his.