In reply to Tiernan:
I've had a recurring problem with a partial dislocation /sub-lux of my left shoulder - it pops out and goes straight back in again. I've done it a bunch of times and in all different ways (the best one was during an overhead press causing me to drop the barbell on my head).
Anyway, I noticed whilst I was at the gym that the feeling I got in my left tricep during certain exercises was very similar to the feeling I get after I've sub-luxed my shoulder, and I wondered if strengthening my triceps would increase my shoulder stability. Six months of weight training later, and I've not only had no more sub-luxes, but I've not really even felt it wanting to go, it feels so much more solid.
I'm conscious that my problem was not anywhere near as serious as what you guys have been describing - it was enough to make me cautious of some activities but not bad enough to consider surgery - but maybe helpful in some way?