Has severe pain on left thigh bone, while walking, plus pain in the right foot-top bone.are these things due to remicade (infliximab) side effects (taken for uc)?

Not likely!: Uc is associated with an arthritis that can cause what you are experiencing. It is called enteropathic arthritis, and is a type of spondyloarthopathy. The Remicade (infliximab) should help clearv this up. Hip arthritis can causes your problem. A routine hip x-ray is warranted. If your doc has no problem with this, Naproxen or Ibuprofen should help.