Shoulder impingement has a particular cruelty at night. You fall asleep fine, roll onto the wrong side at 2 a.m., and wake up with pain radiating from your shoulder into your arm. This repeats until you give up on sleep entirely. The deprivation stacks on top of the shoulder problem and makes everything feel worse than it actually is during the day.
Sleep position matters here more than most patients have been told.
Why nighttime pain is different
During the day you mostly avoid positions that compress the subacromial space. At night you lose that awareness. If you are a side sleeper, lying directly on the affected shoulder compresses the already-inflamed bursa and tendon against the acromion for hours. Even lying on the opposite side can pull the affected arm across your body in ways that pinch the tissue.
The supraspinatus tendon has poor blood supply compared to other tendons in the body. Horizontal position reduces blood flow further. Less perfusion means less ability to clear inflammatory byproducts overnight, which is partly why you can wake up stiffer and sorer than when you fell asleep.
The position that works best
Back sleeping is the most reliable option. It keeps both shoulders in a neutral, uncompressed position. Place a pillow under the affected arm to keep it slightly elevated - this reduces tension on the subacromial structures and improves circulation through the tendon. A pillow under your knees helps you stay on your back through the night.
If back sleeping is not realistic for you, the unaffected side is the next option. The problem is that most people unconsciously curl the affected arm across their chest, which internally rotates the shoulder and shrinks the subacromial space. A body pillow in front of you gives the affected arm somewhere neutral to rest without pulling across the midline.
What makes it worse
Sleeping on the affected shoulder is obvious. Some less-obvious positions cause problems too.
Sleeping with your arm raised above your head - common for stomach sleepers - keeps the subacromial space compressed for hours. If your shoulder is consistently worse on mornings after you slept that way, that is the reason.
Tucking your arm under your pillow or under your body locks the shoulder into internal rotation all night. If this is a habit, a firmer pillow usually eliminates the gap you are instinctively trying to fill.
Stomach sleeping in general is rough for shoulder impingement. It almost always involves the head rotated to one side and the arm in a compromised position. If you cannot break the habit, a flat pillow and keeping the arm at your side rather than overhead reduces the damage.
Before you get into bed
Ice for 15 to 20 minutes on the shoulder before lying down helps with acute inflammation. If the shoulder is not actively swollen, some people find heat more useful - it relaxes the surrounding muscle and can make it easier to settle into position. During a bad flare, ice is the safer default.
Ibuprofen or naproxen taken with dinner reduces overnight inflammation and can meaningfully cut the number of times you wake up during a rough stretch. It is not a sustainable daily habit, but it is a reasonable tool during an acute period.
A pendulum exercise before bed - standing and letting the arm swing passively in small circles for a minute or two - decompresses the shoulder without asking anything of the rotator cuff. It is one of the few things you can do right before sleep that has a direct mechanical effect.
When positioning alone is not enough
Night pain is one of the clearest signs that shoulder impingement has moved past its early stage. If you are waking up multiple times despite sleeping in the right position and this has been going on for more than three weeks, see an orthopaedic surgeon.
A subacromial corticosteroid injection reduces inflammation quickly and can break the pain-sleep cycle when conservative measures have not been sufficient. The effects usually last weeks to a few months. That window is most useful when you spend it actually doing the physical therapy - the injection reduces pain, the therapy addresses what is causing it.
Patients who address sleep position, complete a structured PT program, and modify whatever activities are aggravating the shoulder resolve impingement without surgery the large majority of the time. Getting enough sleep is not incidental to that process - it is part of how tissue heals.
