Back pain is common for a lot of people as they get older. Too much sitting, weak core muscles, accidents that strain the back, arthritis, etc. can all cause pain. For people with Parkinson's, it can be worse because of issues of rigidity or the hunched posture that affects a lot of people.

My issue is my si joints are tight, which makes it difficult to walk
What Is the SI Joint?
Your sacroiliac (SI) joints are where your spine (sacrum) and pelvis (iliac) connect. Your sacrum is the triangle-shaped bone at the bottom of your spine, and your iliac is made up of two fan-shaped bones. They join together at your SI joint to form your pelvic girdle or hips. If you look at someone's lower back, you can see the two sacroiliac joints as dimples on either side of their spine, low across their hips.

The main job of your SI joints is to shift the weight of your upper body to your hips and legs when you stand up and carry it as you walk. They also act like shock absorbers to keep all the structures in your upper body stable as you move around.

Dad had shoulder pain, right shoulder, but it was fixed with a cortisone injection.