
Originally Posted by
vermin
On a rare occasion I've had some oil back out of an injection site - I'd say that's the only time you'd have an issue. I usually wait about 30 seconds with the pin at my full injection length, then withdraw halfway and wait another 30 seconds. This seems to minimize bleeding etc. (I have been concerned that the bleeding post injection is disproportionately oil).
If you look at the amount of oil/blood and use the pin to draw up and splash about .1cc of water next to it I think you'll see that any amounts backing out are actually miniscule. OTOH, quads are some the the largest muscles on the body, larger muscles = better depot, better depot=better utilization of the gear so shoot quads second only to glutes.