Suggest Treatment For Muscle Atrophy When Bedridden

Husband has been bedridden for 8 months after heart valve replaced . His has been in rehab to stretch limbs has finally been able to put weight on his feet with help. Now in hosp for 7 days & with low sodium,MRSA in bone under pressure sore and also wound on chest. Now his legs are showing atrophy and drawn up to waist. After stretching them out when he is put on his side they draw right up again. He knees are really hurting him. What to do. ???