I have a pekin duck that is limping realy bad. Our vet says it's not bumble foot. We think she might have a sprain, or she broke a part of her foot. We can't wait till she's better so she can run with her friends!!
If it's a sprain then you first want to isolate the duck to keep it from running around and give the leg a chance to heal. It is helpful if you provide a tub of water for her to sit in and get the weight off of it. If possible, it's good if the isolation area is where she can see the other ducks so she won't feel lonely.
If the leg is warm to the touch and/or looks/feels swollen then you will want to give it a soak in Epsom Salts - You will need to hold her and keep her from drinking it as Epsom Salts are a laxative.
You can put some ACV (Apple Cider Vinegar) in her water (2-3 Tbls per gallon of water). Then give her some healthy treats such as Kale. Both of these items have properties that are helpful for both bringing down inflammation and added vitamins to promote healing. Plus treats (frozen peas are great) to cheer them up because they are in confinement.
I had a duck that I treated for a sprain this year that took 3 days to heal. But depending on the severity, sprains can take from a few days to several weeks.