If chicks have hatched like this then probably nothing can be done,as bones have probably fused in this position. You could try checking for a slipped tendon,gently roll leg between fingers see if you can feel slipped tendon,it will feel loose/springy almost like an elastic band or you can run thumb down back of leg from hock to shank feeling for slipped tendon. If you feel a slipped tendon press down you can feel it snap back into place,do this several times a day or wrap to keep in place.
With leg issues immediate treatment is the key to fixing problem b/c the longer it is left,the less chance of success.