What Does Painful Swelling In The Legs And Ankles Indicate?

hello, my father was admitted to a hospital for pneumonia. he was septic, and had a bad infection im his lungs. two days after his admission he began to feel better but his feet and legs began to swell and his ankles are very painful to the touch. thought it was gout, but ruled out cuz his uric acid levels were fine, tested for lime, but not that either. its been 5 days now and no one knows what it is. im thinking it it could be a reaction to some of his anti biotics but still no answers.. any thoughts?