I've had two chickens that had broken legs. One was broken at the knee joint and the other was a compound fracture of the lower leg. Both I have rehabed backinto the flock. Initally I had them seperated in their own cage, naturally with food & water, medication for pain and an ABT too. Nice & quiet so they could heal and recover from the hurt & shock of a broken limb. I had brought them each into my house and placed in the sunroom. A heated/cooled place that is rarely used but they could see out of the cage at daylight or dark. A real nice place for a chicken if I say so myself. I initally wrapped each leg with a gauze then vet wrapped to stabilize the break. I kept this on for a week at a time, changing each week to look at the leg & replace with clean materials. Sure they didn't like this, but eventually they were able to move around somewhat. Eventually they got better and I was able to remove the vet wrap once and forall. They do limp, but not noticable and itn't doesn't interferr with their ambulation.
You never know until you try. So go for it.
Jan