Getting the patient walking again

An old fellow came into the hospital truly on death's door due to an infected gallbladder. The surgeon who removed the gallbladder was adamant that his patients be up and walking in the hall the day after surgery, to help prevent blood clots forming in the leg veins. The nurses walked the patient in the hall as ordered, and after the third day the nurse told how he complained bitterly each time they did. The surgeon told them to keep walking him.
After a week, the patient was ready to go. His family came to pick him up and thanked the surgeon profusely for what he had done for their father. The surgeon was pleased and appreciated the thanks, but told them that it was really a simple operation and we had been lucky to get him in time. "But doctor, you don't understand," they said, "Dad hasn't walked in over a year!"