Stifle problem in older horse
I lease a 17 yr old arabian, and i recently noticed that her stifle seems to 'pop' when she moves and it makes a popping sound. I've heard that she's had stifle issues in the past, but this seems a little strange. She is older, and it is winter, im wondering if its possible that the cold weather is affecting her? It really doesn't seem to bother her much, but i dont want to push her. I havent had her under tack since i found out about it. I do some barrels on her, no fast at all really, but im wonering if doing that may have led to this as well. I know there are some joint supplements for older horses during winter, does anyone have suggestions about these? Her stifle problem has kinda got everyone at my barn stumped, but no one seems to think its a huge deal.
any help is greatly appreciated! thank you