As strange as this may sound, I have found that good old Mucinex, that is, active ingredient *guaifenesin, * really helps amazingly with my stiff and achy hip/haunch muscles, tendons, and ligaments. I suffered a very minor injury years ago, but the area around it became stiffer and more painful over time. I noticed once when I had a bad cold and was taking the usual cold remedies that my hip area felt suddenly better. I narrowed it down to the effect of guaifenesin.
Since then, I have found that many fibromyalgia sufferers also report an amazingly beneficial effect of guaifenesin on their stiff muscles! It really does work, is sold over-the-counter, and I notice no side effects. They make 600mg tabs, but even 1/2 per day really helps me.
I hope it helps you too!!