What is frozen shoulder?
Frozen shoulder is a condition that affects your shoulder joint. It usually involves pain and stiffness that develops gradually, and gets worse. If you have a frozen shoulder, you’ll likely feel a dull or achy pain in one shoulder. You might also feel the pain in the shoulder muscles that wrap around the top of your arm. You might feel the same sensation in your upper arm. Your pain could get worse at night, which can make it hard to sleep.