I do believe that the supplements have some effect, I do not believe they will fix a structure problem.
I think if an animal has a slight hitch in their get along they can help, I don't think their going to help an animal that has bigger issues. I know people who swear by Lubrisyn (or it's generick contour part) but it is not something you can just give at the end it is something you have to start early on stick with.
We had one with that they helped did not make him perfect but did make him better, without it he may have been a wreck, did not take the chance.
Along with supplements they need to get out and move, I think more problems arise this time of year since animals are starting to be tied, stalled or put in a cooler about this time of year, they tend to start showing problems. Make sure they have plenty of room to get out and move when they get kicked out at night, if you do not have a large run, get out and walk them for at least a good half hour or so before penning for the night. I think the exercise is key to staying sound.