Of all the symptoms people describe in a shoulder clinic, this is the one that most reliably wears them down. The shoulder is manageable during the day. You work, you drive, you get on with things. Then you lie down, and by one in the morning you are sitting in a chair in the dark wondering what is wrong with you.
Nothing sinister, in almost every case. There is a simple mechanical reason, and knowing it helps.
The explanation
The tendons of your rotator cuff pass through a narrow gap between the ball of the shoulder and a bony arch above it. When you are upright, the weight of your arm applies a gentle downward pull that keeps that gap open. It is small — a few millimetres — but it is enough.
Lie down and that traction disappears. The gap narrows, and an inflamed or torn tendon is compressed between two pieces of bone. Add the fact that at night there is nothing else competing for your attention, and a moderate ache becomes the only thing in the world.
What it usually turns out to be
- Rotator cuff tear or tendinopathy
- The commonest cause by far. Night pain plus weakness lifting the arm, plus difficulty reaching overhead. Often no injury at all.
- Frozen shoulder
- Severe night pain in the early months, but the defining feature is stiffness — the shoulder will not move, and nor will it move for someone else. Outward rotation goes first.
- Impingement from a bony spur
- A spur on the arch above the tendon narrows the gap further. Pain in a specific arc of movement, and at night.
- Shoulder arthritis
- Less common than in the hip or knee. Grinding, progressive stiffness over years, and an abnormal X-ray.
- Referred pain from the neck
- Worth ruling out. The clue is pins and needles or numbness travelling past the elbow into the hand, and pain that changes with neck movement.
How to sleep, tonight
- Sleep semi-upright — propped on two or three pillows, or in a recliner if you have one. This restores some of the downward traction on the arm.
- Put a pillow under the elbow of the painful arm so it is supported rather than hanging.
- Hug a pillow to your chest if you sleep on the good side, which stops the painful arm dropping forwards across your body.
- Avoid sleeping with the arm above your head, which closes the gap further.
- Take simple analgesia about half an hour before bed rather than at the moment you cannot bear it.
- Keep the shoulder moving during the day. A shoulder that stops moving stiffens quickly, and stiffness hurts more.
When to get it looked at
- Night pain that has cost you sleep for more than three or four weeks.
- Weakness, not just pain — particularly if the arm drops when you try to hold it out to the side.
- You cannot lift the arm at all, especially after a fall. This may be a large acute tear that does better repaired early.
- Progressive stiffness, which points towards a frozen shoulder and has stage-specific treatment.
- Pins and needles into the hand, which suggests the neck rather than the shoulder.
- A hot, red, swollen shoulder with fever — this needs assessment the same day.