Recently, Mulberry4355 presented what may prove to be an important aspect of how PD is conceived, visualized, understood (at least for one or more subgroups).
Parkinson'so is not a disease?
Some informative links:
"In fact, whether you run, bike, dance, practice yoga, or just hang out on your couch, your psoas muscles are involved. That’s because your psoas muscles are the primary connectors between your torso and your legs. They affect your posture and help to stabilize your spine."
"Welcome to CoreAwareness,™ an educational website dedicated to understanding the Psoas through enhanced somatic awareness."
Psoas Major: a case report and review of its anatomy, biomechanics, and clinical implications.
Parkinson's disease with camptocormia.
Postural & striatal deformities in Parkinson's disease: Are these rare?
[personal anecdote, 2005] I had taken a long hike toward the base of a mtn climbers' steep ascent. Could not see westwards. Clouds began spilling over the ridge line. Lightning started. Time to descend somewhat. Lightning was moving slowly along an adjacent moraine. I kept moving, with my fanny back and full water bottles on my front side, my camera backpack in place. With hiking sticks I made good time. Ahead of the lightening. The jog/walk sprained my back. Within a year or so, I developed severe leg cramps and began slow fecal transit. To this day, I use a rolled towel behind my back while I drive. A cylindrical pillow in an easy chair also helps. Had I sprained my PSOAS muscle(s)? Probably. Was this an etiological factor in my PD or in hastening its appearance? Maybe. Consistent with some of the links Mulberry4355 posted.