Targeting the hips and lower back with strength and flexibility exercises can improve your posture. When your hips and lower back are stronger, it helps to improve back pain and knee pain. It also helps reduce injuries to your back and knees. Another benefit would be stronger bones and muscles.
Strength and mobility can be improved for just about anybody no matter what their condition. As long as you have your doctors permission and are healthy enough to exercise, you can even begin doing exercises in your bed, then gradually progress to chair exercises, then to more advanced exercises.
The idea is to be as active in your life as you possibly can be. Enhancing your quality of life will make life more enjoyable. If you have been inactive for a while, begin to strengthen and condition your muscles again with mobility exercises.