Debilitating pain 6 months after knee replacement

My husband had knee replacement surgery six months ago. The knee is still swollen, hard, and very warm. He still has chronic pain. He's at a constant 3-4 level most of the time, with episodes that shoot the pain up to 9 -10 range every day -- every damned day! -- that bring him to tears. And this is a man who's had broken bones, suffered concussion, and had a total hip replacement and was back on the golf course in six weeks. He's had every blood test you can think of to rule out infection. He's been X-rayed and scanned to rule out anything else. And we're told everything with the new joint looks fine, so keep doing what you're doing and it will get better. He does PT. He elevates, He ices. He does deep breathing. We've been to a pain management specialist who's fiddled with his meds and done laser therapy. And nothing works to bring the pain down. it's not getting better. Any ideas or recommendations?