OM, apparently those muscles can mess you up all over. My left hip would start to feeling like it fell out of the socket. I finally learned to stretch my calves when that happened and it made all the difference in the world. I also started walking more, and I do it on a pretty steep hill. I'm getting better, but it's really all about getting out and walking more. For me, the pack doesn't add much bother. I'd get to hurting just as good without it.