I've only ever encountered one slipped tendon case...bilaterally. I got one of the legs to mend, but the other didn't and I had to euthanize. I was working with that bird for two weeks. You have to act quickly with it, because the bones can easily outgrow the tendon. There's somebody around here who does peafowl that's pretty knowledgeable on it (peachicks apparently get slipped tendon a lot -- they're springy little birds). I suggest searching around the peafowl crowd -- He eventually went to the vet, who gave him a better idea of how to wrap the leg. That might be what you have to do. I can see how ducklings might be different - with the bulkier legs and also the ability to /swim/ which is good therapy in general...Good luck.