Knee Pain, X-ray Shows Reduced Gap Between Bones In Knees. History Of Ligament Problem In Knee. Advice?

My husband had a ligament problem in his right knee since his college days and the same was left unattended and recovered on its own, he faced the same problem nearly 5 years back and was given necessary medication and physiotherapy and he recovered. In 2010, the pain restarted and the xray showed that the problem now was with the miniscus and he underwent a minisectomy, followed by physiotherapy. All was well till a few weeks back when both his knees started paining and now the xray shows that the gap between the bones in the knees have reduced. He has been advised rigorous physiotherapy for 3 - 4 weeks and also been asked to reduced weight and then it will be taken further, a humble request to you to advise what would be the best way to get my hubby back on his feet without the pain. He will complete 38 years (age) this month, he is 5.10 ft and weighs 83 kgs.