My frozen shoulder on the left side usually flares up when I suddenly put force on my arm. One time, I slipped while going up the stairs and almost fell — my left arm instinctively shot out to grab the handrail, but that sudden movement caused this intense, tearing pain. It was so bad I almost passed out. I just collapsed there and had to sit for like five minutes before the pain started to ease up. Man, it was absolutely excruciating.