Glucosamine and fish oil are usually very well tolerated and may help take the edge off. Outside of that try taking baby steps, incentivizing with treats, and trying to get a little further each day working your way up to it, or making more frequent shorter duration walks. Another alternative is to look for dog friendly places where you two can stretch your legs that are heated (perhaps a nearby mall). There might not be a 100% solution that works but maybe there's something that at least provides some incremental improvement. I wish you both the best of luck in figuring it out
