Reviewed your symptoms. History of lower limb surgery with metal implants. Now coming to present symptom of pain and swelling the ankle for 6 days, could be due to injury
sustained recently leading to sprain
. But if you do not have any history of injury then you need to be evaluated for infection. Because presence of metallic implants or prosthesis
would provide focus for infection. Anyway you need to consult a Orthopedician (Bone and Joint Specialist) to get yourself evaluated to for cause of your pain and swelling as early as possible.