Hey I'm not sure about this, but i use to hook like crazy and now that i don't i can say that it has helped my elbow. I've torn my ocl a little bit, aka micro tears, (tommy johns). This was when I was in college my senior year half way though the season. To finish out the season I had to rest and change my mechanics and one change was to stop hooking. But ever time i would hook I started to notice that my wrist muscles (mainly around my elbow) would tensing up, then relaxing and then tensing back up right before release. So I feel it was like I was doing double the work of a normal throw. Now I'm not saying that hooking will tear your ocl, b/c for one everybody is different, two others do it still, and three I feel my injury was due to other problems. All i can say is I've noticed a difference when I stopped. Personally I don't think that hooking will lead to injury, but I do think it does put more stress on your arm in the long run.