Well... I have this problem.
One of my RIR roosters was injured during the fight with other rooster. Some kind of muscle injury.
I separated him from flock and seems that after 2 weeks or so he don't feel any pain in his leg but there new problem arise.
While his leg was injured he was jumping only one when he was moving and now after additional 2 weeks passed I noticed that he still don't wanna walk on this leg... I brought him to doctor and he says that he have problem with the muscle at the moment as he wasn't using this leg long time.
I try to give him some massage every day and try to stretch this leg/muscle but after 5 days there is no change in his condition.
Any advice ?