Here is the text from something I wrote a while back:
If it is a sprain, make an Epsom salt compress. 2 tablespoons Epsom salt, half a cup of warm water. Soak a clean cloth in that. Gently hold the duck and wrap the cloth around the leg and foot. Wait patiently together for ten minutes if you can both go that long.
Do this twice a day.
Epsom salt is a laxative, do not let the duck drink or eat it.
Some members put the Epsom salt water into a flat-bottomed dish and stand the duck in it, holding the duck gently. Remember, no drinking the water.
I like to use comfrey and St. John's wort on the outside of the leg and foot for sprains. I have a cream called Traumeel that has those things in it, and I put a tiny dab on the leg at night (they don't swim at night). - added note - Traumeel has been reformulated, it is now called T-Relief.