I had back pain for years and always woke up in the morning with aching joints, it never ocurred to me it was because of my matress, until my boyfriend slept in it and could barely straighten up in the morning.
Anyway, I purchased a double size memory foam matress and it was pretty good, although expensive at �500. My aches and pains subsided to a degree. When I moved in with my boyfriend, he insisted we purchase a Tempur memory foam matresses as he'd been used to them for years, so we purchased a Superking size one. It was very costly at �1400 and has 8 inches depth of Tempur memory foam.
Well all I can say, it's the best thing we've bought, it cradles every part of the body, supporting all the body's contours. Since sleeping on the Tempur, I have never suffered any kind of aches and pains and I always get a really good night sleep.