That’s great! Encourage him to keep up the good work!
If you can motivate him to become more active such as taking walks daily, maybe a couple short walks, he’ll be amazed at how much better he’ll feel. The increased circulation from the exercise will help his entire body. His wound will heal faster, his new hip will flex better and overall he’ll have less muscle soreness and stiffness and his outlook will improve.

Is he feeling a little depressed with all the changes of this past year?