Background on my horse: My gelding is around 20 years old, Morgan/Quarter Horse. Has had one major health scare almost 2 years ago but has fully recovered, and otherwise is healthy. He last saw the vet a few weeks ago for a sheath cleaning and he is due for a hoof trimming. When the vet saw him, she said his weight is great. He lives with one other horse, a mare, and they get along fine. He has 24/7 turnout with shelter and is not ridden often. He is getting hay along with grain + Acti-flex Senior and whatever green grass remains in the pasture. We live in NC, not in the mountains, so winters are fairly mild compared to other places; it ranges from 45-60 degrees average during the day and 20-40 degrees at night. He becomes a mammoth in the winter and I've never seen him shiver so I don't think he is cold. He is very sweet when it's warm. You can love on him all day and all night and he will want more attention. Come winter, he can barely tolerate people being around him. He can be rather unpleasant to deal with from November-March. He doesn't actually DO anything, no biting or nipping or kicking. He just makes a lot of grumpy faces and head swinging when petting, brushing, standing near him, etc. I've always just ignored him when he does this. There are times where no one will be standing near him at all, and he'll suddenly put his ears back at nothing for no apparent reason. This started maybe 5-6 years ago. It took me a few years to catch on to the fact that it seems seasonal, and then I asked the vet about it. She said from how his back legs seem a little stiff and his age, it's possible he has arthritis in his stifles or hocks that is aggravated by the cold and recommended I start him on Acti-flex Senior. He's been on it for nearly 2 years now. It seems to help his attitude a little bit but not by a lot. Is there anything else I can do for him to help ease arthritis? I've never dealt with a horse having arthritis before. I am willing to ask my vet for more solutions besides an oral supplement. Could his foul mood be caused by anything else?