You managed the day fine. A few twinges reaching for things, nothing dramatic. You went to bed at a reasonable hour. And now it’s 3 a.m., you’re lying there with a deep ache down the outside of your arm, you’ve tried both sides and your back, and you’re doing the calculation about whether it’s worth getting up. Night pain is one of the defining features of shoulder problems. It’s also one of the most disruptive, and one of the most diagnostically informative — because which shoulder problems wake people, and how they wake them, differs in useful ways. Here’s why it happens, what your particular pattern suggests, and what actually helps.