If there's nothing major like muscle tear/huge amounts of scar tissue etc then it's suprisingly effective. If it is going to make some kind of positive change to your condition then you might feel at least a bit of improvement pretty much straight away or def the next workout.
I tried it for a bout 3-4 rounds of 90 secs every other day.
The general recomendation seems to be a few vigourous 20 mins sessions(say 2mins on, 2 mins off) and then do it once during the workout immediatley before a movement that pisses off the joint.
After a couple weeks it can make a pretty big difference