What Causes Swelling And Redness Along With Pain In Foot?

My 29 year son has 4 screws in his foot from an injury repaired 10 years ago. He has also developed arthritis in his foot. Now for 4 days has had swelling and reddness and pain to the foot. This pain is different that his chronic arthritic pain. He has no known injury. Otherwise healthy. Could he be rejecting these pins? Would the rejection show up on xray?