There are two places that you are going to have to work on him to get rid of this. One is the bottom of his foot. Give him a nice massage and then put both of your thumbs, side by side, at the back of his arch right in front of the heel. Press in firmly as far as he will let you and hold. After 30 seconds have him raise his toes up as far as he can, release the pressure but have him hold his toes there for another 30 seconds.
Move to the top of his foot and front. Right where the foot and leg meet there is a little opening that you can feel there. Take two fingers and spread them across the opening and press in and hold that pressure for 30 seconds. After the 30 seconds have him extend his foot down, slowly, as far as he can. Release the pressure but hold the foot there for another 30 seconds.