How much did you drop by to get to 10mg? A fairly large drop can cause new pain/stiffness. Is the pain and stiffness only in the morning or all day? If it's mainly in the morning, a split dose might help.

Everyone who splits their dose to control morning pain seems to do it a bit differently. Most of the dose is best taken in the morning when the body would normally produce cortisol. From the advice I found on split doses before doing it myself, no more than one third of the dose should be taken later in the day, and not so much in the later dose that sleep is affected.

When I was up around the dose you're taking I took most of the pred in the morning and 2mg with dinner and it controlled morning pain. Currently I'm down to 4mg, taken as 3mg morning & 1mg with dinner and there is no pain, just occasional morning stiffness or slight aches which pass.