That leg just looks so unusual to me. Is there any chance that the chick suffered from frostbite in the feet in recent weeks? Or could there be a plastic band around the leg that has become embedded in the skin, cutting off circulation? This happens pretty often in chicks, and those bands tighten as the chick grows, not easily seen, but the circulation can become cut off. Paralysis then could happen. Please probe around the leg with some tweezers to look for a band, and cut it off if there is one.