If you or someone you know has or keeps getting frozen shoulder, I think I found the cause.

Sleeping on your side.

Drs will say they don't know the cause.

When you press on your shoulder for many hours of sleeping, it strains the ligaments in your shoulder. That causes inflammation.

I've been sleeping with a wedge pillow under my torso for 2 months. I let my shoulder hang off the end. I have 2 pillows stacked to support my head.

Very comfortable. Great sleep.

Frozen shoulder is gone!

@jurban It probably aggravates it. I sleep on my left shoulder and got horrible frozen shoulder in my right shoulder mainly and only a little in my left. I now sleep with a pillow under my body but I also shift from side to side. I'm in the 'numb' stage for years but it helps with keeping it slightly more movable.

@jurban I believe the seeds of my frozen shoulder started 40 years ago in the military when we were putting up a 180' tower in sand. The stakes started failing, the two men were not paying enough attention and got jerked off their feet and it was just me holding that sucker upright with one of my men at the apex. I believe it took many years for that damage to fully come home to roost. No regrets though, the guy lived.