You have just described a dilemma faced by many family members of someone who has had a total knee replacement or total hip replacement. The reason for the apparent difference between perceived function and actual function appears to be one thing: pain.
And even as the pain subsides (decreases), patients don’t always recognize or report a sense of improved function. They may be able to walk farther and faster, but even a small amount of pain makes it seem like less. There are many ways to help patients see themselves in a more positive (or realistic) light.
Special tests of function can be given to the patient by the physical therapist. Walking, function, and activities of daily living can be measured. Once the patient sees the functional score on paper, they may see themselves more as they are and perhaps improve their overall outlook.
Another tool is a journal or log of daily activities. This can include how far they walked (or how many minutes they walked). Number of stairs, amount of time on a stationary bike, and even daily activities accomplished can be recorded and compared week-by-week.
With time, it’s possible that things will still smooth out. By now, your wife has completed the standard rehab program. Continuing with a fitness program or regular exercise of some type is always advised. Keeping a log of the advances made in the fitness routine is another measurable way to chart progress.