I have one that sounds the same. I hatched its self though with no problems though. After talking with people I thought it might be a slipped tendon but now I think it is in the hip. Does yours rock back with the foot up? Also I am seeing the foot looks a bit swollen but the toes work fine. I can see that using the fix for splayed legs will work as it holds the leg up and out, not just out. Other than manipulating to check the tendon and see if I could find the problem I havent done anything. I was hoping it would improve but it is looking worse ;(
I would put the Bandaid hobble on him now. After the first couple of days the hip starts to set and there will be no fixing it (if it can be fixed) later.