I've had it about 6 years. It comes, and it goes, but it is always there. I want to stress that surgery is not the only option for dealing with this injury. In less severe cases, correcting the mechanics that cause this injury can fix it or at least keep everything "together". I've had times where it's gone away just about completely.
Triggers:
Icy/slippery conditions
Uneven terrain
Long runs
Sprinting (but see below)
Treadmills
Tight hamstrings
Tight hip flexors
Track work on curves
Weight gain
Lunges/split squats
High mileage
Not warming up enough
Exercises/stuff I've found helpful:
-http://www.groin-hernia.com/herniabible/exercises.html
-Sprinting-with good form, and focusing on keeping the hips forward and "up" with glutes firing, I think sprinting can be really, really helpful.
-Plyometrics help
-Weight training (the glutes NEED to be activated/triggered and this is one of the best ways to do it...just be careful)
-Adductor and abductor strengthening and/or stretching
-Leg raises on machine (working lower abs)
-diet...really nailing this part of the equation really helps. Plenty of lean protein and greens/fruits.
-Bagging a run if it starts acting up or legs tighten...it's just not worth doing damage for minimal fitness gains. Suffering through a run isn't worth it short or long term.
-pace doesn't seem to matter...fast or slow or medium, all that matters is HOW you are running mechanically.
-balance/core stuff
-hip extension stuff (this injury is basically the lower abs being ripped downwards due to poor hip flexibility during hip extension...tightness in the hip flexors, glutes, hamstrings, abductors or adductors can all cause this.
Everyones hips are different, but everyone shares some similar characteristics for this injury.
Basically get the hips firing correctly (MUCH easier typed than done!) and STABLE and this injury goes away. Strengthen and/or loosen the core area as needed till the act of running is NOTHING to it.
Some of these exercises will not be doable/help for more advanced cases.
Rest doesn't really help much at all for this injury, I've found.
Neither does running through it, if you don't fix the mechanics that are causing the tearing.