He should practice Yoga daily with total focus on mulabandha, deep breathing, and one pointed concentration. He should move briskly between the postures. He should do nothing that injures his legs, (or anything else). Of course Rolfing and massage will also be beneficial as well (for all of us as well as him...lol).
One should not mistake the purpose of this and every system of Yoga, which is to increase prana. Nothing decreases prana more than pain and injury. Maybe over the years, his legs will get looser, or maybe they won't, depending on a lot of factors. Nevertheless, he can experience all of the benefits of Yoga. He is at no disadvantage and should be clearly told this. What's important is what's invisible!
Yours in Yoga,