Most of my problems are on my left side too! I have no idea why it's mostly on one side like that. I do have some problems on the right side but, the left is alot worse for some reason. This is a good question for my rheumy when I see her.
Most of my achy joints are on both sides except for my fingers. My right hand is much worse which is sorta wierd since I'm a lefty. So I think I'm a unilateral and a bilateral.