I took the swan to a vet as you suggested and she diagnosed it with perosis or slipped tendon. The prognosis does not sound good. She said he was too old to bind the legs and surgery was the only option (which was no guarantee it would work). We have supplemented the food with extra nutrients and taped the joint (like a figure 8 ) in hopes it will improve. The vet said it is not painful but it doesn't seem like quality of life if going to be favorable. Also wondering if the swan mate will reject him when they get older. Any suggestions on how to improve his condition? Should we consider Euthanasia? Thank you for your insights.