Over the years my knees have given me a hard time on Horseback hunts. I stay in very good shape and still they bother me. The last couple years I started to force myself to do more leg stretching throughout the year. I found that for me one stretch in particular has made the difference and I have much much less discomfort when riding now. The muscles and tendons that run on the outside of my legs and knees are what get sore. The stretch that has fixed this for me is to squat down like a duck and stay there a long time and just get my rear end lower and lower and stretch out my knees. When I first started I could only squat down about three-quarters of the way because my knees wouldn't allow me to go any lower. I've gotten to the point where I can squat all the way down with pretty much no discomfort. I was pretty amazed on our elk hunt a couple weeks ago how great my legs felt on the horse thanks to my improved flexibility. This stretch may or may not help you but my point is that having your legs and lower body be nice and stretched out before heading on a horseback hunt can make a huge difference in your comfort and enjoyment.