What Causes Leg, Foot, Ankle, Shin Area And Knee Weakness With Pain?

Hi, may I answer your health queries right now ? Please type your query here...51 White Male. Fairly active. Have Ulcerative Colitis; was on IMURAN and now REMICADE. About 3 months after starting IMURAN I started to have a weakness in the right leg. Evidenced by pain that moved up from the middle of my foot to the knee. But only when weight is on it. Sitting down and moving my leg without weight on it there is no pain. I will walk sometimes for a while and it gets better. Then I sit down and get up 10 minutes later and its back again. I stopped IMURAN in June and it seems to have gotten a little better. It will hurt and be weak in the foot, ankle shin area and knee and it moves around.