I woke up with slightly annoying neck pain one day, like a stiff neck, and didn’t think anything of it. Went to sleep and woke up to the most intense rotator impingement with excruciating pain with no relief from any medicine or any other forms of treatment. Went to see my doctor, who set me up with an orthopedist, and my MRI is scheduled. The problem is, I went from not being able to use my arm at all for 3 days straight, to waking up feeling almost much better. What causes a flare up that intense?