Complex Regional Pain Syndrom

I have a friend who has CRPS after a surgery from a ruptured Achilles. He has made it through rehab after some pretty intense pain but now is cleared to start doing some strengthening after losing 40lbs of body weight. This is the first time I have dealt with this condition directly. He has asked me to help him gain some strength back. I know this is a real condition but how does this fit into the Bio Psycho social model of pain and are there strategies I can use when helping him to reframe his pain experience while not dismissing or ignoring pain he may be experiencing?

Thank you for your thoughts,

Nate