Do you have arthritic symptoms like a sore back, joint pain, swollen digits, morning stiffness that improves once you get moving, etc.? If so, tell your doctor. It could be psoriatic arthritis. While most treatments benefit both psoriasis and psoriatic arthritis, some treatments are considered more effective in certain cases than others, and there are a few that do not have FDA approval (not yet, anyway) for one or the other condition.