I have a 74 year old male client who is awaiting a knee replacement (the other knee has already been replaced). He has had numerous surgeries (quadruple bypass, brain stem, removal of fluid from his knee, etc.) and is a real trooper. He cannot stand for very long so I have been doing most of my workouts with him in a chair. He would like to build more leg strength so he can stop using his walker and use a cane but it is very difficult to work his lower body with strength building exercises. Any suggestions on what I should be doing to (1) build his leg strength up and (2) keep him from getting frustrated until he gets his knee surgery?
I am on the assumption that you have all the medical clearance you need.
You have to think specificity. If he wants to get better at walking, you have to start doing more exercises standing. Find a safe environment where there is no risk of falling. Standing up from a chair ever which way is probably an exercise for him. See how many times he can do it. This will also give you something quantifiable. Have him do mini squats. Sit down to rest in between as necessary but then stand again.
He is in a challenging situation, and there is currently only so much you can do. After the surgery, he will be initially under the care of a physical therapist, and you should hook in there as quickly as possible so that you can assist him seamlessly after he has been cleared for exercise.
I wish you and him good luck.