Sounds like he has some bad tendinitis in his hands. This can become permanent if not treated. He should see an orthopedic hand surgeon for treatment and see if he needs surgery to loosen up the tendon coverings in his hands. My brother-in-law had surgery last year because his hand did close up like a claw and he could no longer get it open. Worked beautifully. He's going to have the other hand done shortly.
But it's better to get it treated early than wait for it to get so bad they have to operate. But at least you know it's treatable.