Many people I know, some with Pd and others not, have terrible problems getting into or out of a chair. I have shown every one of them how easy it is, if done properly. The main problem is, not having the weight of the body over the feet, when getting up and sitting down.
What do I mean by this? If we sit in a chair that does not have any space between the underneath of the seat and the floor, like most armchairs, then our feet are out in front of us and when we get up, we have to push with our arms to get us into a position where our legs can get us upright. It sounds so simple, and it is!
If we sit on a kitchen chair, which normally has space between the underneath of the seat and the floor below, then we can push our feet back underneath the chair and lean our torso forwards until our heads are over our toes. Then, an only then, should we try to get upright.
If you still battle to stand up, it is nothing to do with Pd, it is simply a lack of muscle tone, which can be rectified by exercise. You should not need to push yourself up with your arms!
What exercise do I mean? Practice standing behind a kitchen chair and holding on to the chair with your hands. Then practice bending you knees as low as you are able and holding that position for a couple of seconds before rising back up again. Do that up to ten times, at least twice a day. You will soon find that you are able to go lower and lower down, until you are doing a complete squat. Imagine that! Won't you be proud of yourself?
The maxim here is, WHAT YOU DON'T USE, YOU LOSE! Age has nothing to do with it. Any person at any age can exercise and get stronger, unless that person has some other physical problem.
Good luck everyone!