Perhaps your husband is depressed. Surgeries can contribute to bringing people down. If you have not done so already, you might talk to him about his feelings about the surgery and plans for the future in an open, curious way.
If he is lying around the house a lot, you might think up small, fun activities the two of you can do together, just to get him going again. (I know those will be limited since he can barely walk.)
Perhaps he would talk with a therapist if the two of you went together.
Best of luck!