question: Hi: I have been diagnosed with erythema nodosum, I had a total hip replacement in September and in December these nodules started showing up on the back side of both calves. My doctor has eliminated several possible causes; Lymphoma, Rhumatoid arthritis, lupus, strep infection. I am wondering if they could be caused by an allergic reaction to something or could there be a hidden infection from my surgery. Thanks for your input. Pam, age 67