There's two authors who write about getting lame animals back on their feet through diet, and one of them (can't remember which) surprised the vets by getting sheep back onto their feet after they had been walking on the ankles with all four feet. The changes were rapid, and only effected through diet. I've seen and dealt with sheep in this position, too, and diet can do amazing things. Anyway, the two authors are: Pat Coleby, and Juliette de Bairacli Levy. Highly recommend both books though one's more specific to Australia. The other's more specific to Europe. Probably not that relevant to your lamb since it's an injury most likely, but can be relevant for general help. Best wishes.