What usually causes itStrong evidence
The NHS says elbow and arm pain is not usually a sign of anything serious, and at night the usual causes are the same as by day. Tennis elbow (pain on the outside) affected 1.3% of 4,783 Finnish adults aged 30 to 64, and golfer's elbow (on the inside) 0.4%; both were commonest at 45 to 54 and were linked with smoking and with repetitive, forceful arm work. The NHS says tennis elbow pain can range from mild discomfort to constant pain that can affect your sleep, and US orthopaedic surgeons list pain at night among its symptoms.
Irritation of the ulnar nerve at the elbow (cubital tunnel syndrome) is the second commonest trapped nerve after carpal tunnel syndrome; in the UK Biobank it was linked with smoking, diabetes with nerve or small blood vessel problems, being male, carpal tunnel syndrome, osteoarthritis and rheumatoid arthritis. A swelling on the point of the elbow (olecranon bursitis) can follow leaning on it for long spells or a knock. Primary elbow osteoarthritis is uncommon, affecting 2% to 3% of people, mostly men, first noticed at about 50 on average, and more often in manual workers, weightlifters and throwers. NHS inform says elbow pain can also come from the neck, even without neck pain.
Sources 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
Why the elbow can hurt more in bed: what's knownEmerging evidence
Bending the elbow stretches the ulnar nerve around the bony bump on the inside of the elbow and reduces its blood supply. US orthopaedic surgeons say many people sleep with their elbows bent, which can aggravate the nerve and wake you at night or in the morning with your fingers asleep, and UK hand surgeons say sleeping with the elbow habitually bent can make it worse. A swollen bursa on the point of the elbow is sore to lean or lie on, and the NHS suggests extra cushions around the joint while you sleep.
Poor sleep was reported by 71.7% of 46 people with long-standing tennis elbow, more than in people without it, and went with more pain. With elbow arthritis, pain is typically at the ends of the movement; in more advanced arthritis, pain at rest and at night is more common, a specialist review says. Sleep was disturbed in 56.5% of 186 people with a trapped nerve in the neck, and the NHS's advice for neck pain is a low, firm pillow, your head level with your body, and not sleeping on your front.
Sources 11, 12, 13, 14, 8, 15, 16
Tennis elbow at night: an idea to try, not a finding
Why tennis elbow aches at night isn't known. One US surgeon noticed that many of his patients felt worst on waking and suggested that sleeping on your side with the arm overhead presses on the outer elbow. In his look back at 39 patients, the 33 who kept the arm down at night, with a loose tie from the wrist to the thigh, all improved within 3 months, and the 6 who couldn't keep the tie on didn't.
There was no comparison group, the tie disturbed some people's sleep, and no trial has tested the idea. Keeping the arm by your side, or resting on a pillow in front of you, costs nothing, so it is worth a try, but it isn't a proven cause or treatment.
Source 17
Pain, sleep and the body clockEmerging evidence
Sleep and pain affect each other: in studies that follow people over time, sleep problems predict new and worse long-lasting pain more strongly than pain predicts poor sleep, a review found. In a laboratory study of healthy volunteers kept awake under controlled conditions, pain sensitivity followed a daily rhythm, highest in the middle of the night and lowest in the afternoon. That study wasn't in people with pain, so applying it to elbow pain at night is our inference. The NHS's sleep habits, and talking therapy for insomnia that lasts, are the tools for the sleep side.
Sources 18, 19, 20
When night pain needs checkingStrong evidence
The reassuring pattern, in our reading of the sources: pain that changes when you change position, eases when you move the arm, and is linked to what you did that day. An NHS trust's tennis elbow leaflet lists constant night pain that stops you resting or sleeping, unexplained weight loss, unusual night sweats, a high temperature or feeling unwell, a hot, swollen joint, numbness or pins and needles, and losing grip as reasons to see a doctor straightaway. The NHS says see a GP for bone pain that is worse at night, and NHS inform asks you to contact your GP about elbow pain if you have ever had cancer or an inflammatory arthritis. A swollen elbow with a very high temperature can be an infection and needs help the same day.
On its own, night pain is a weak sign: at a back pain clinic, 213 of 482 people had night pain, 90 of them every night, and none was found to have a serious disease. That study was in back pain, not elbow pain.
Sources 21, 22, 10, 1, 23, 24
Tests and scansEmerging evidence
Tennis elbow is diagnosed from your story and an examination; US orthopaedic surgeons say a magnetic resonance imaging (MRI) scan may be used to check the tendon or rule out other problems. For the ulnar nerve, X-rays and nerve tests may be used, but in a Swedish trial 76% of people with typical symptoms had normal nerve tests, and 75% of those with abnormal tests improved anyway, so routine testing seemed unnecessary in mild cases. Arthritis is confirmed on X-rays, which also show bone spurs and loose pieces. Fluid may be drawn from a swollen bursa with a needle to check for infection or gout.
Sources 3, 12, 25, 9, 8, 13, 7
How it usually goesStrong evidence
Tennis elbow mostly settles within a year: in a Dutch trial, 83% of the people who waited and 91% of those who had physiotherapy were successes at a year, and an NHS trust tells patients most people are better within 12 months. Mild ulnar nerve symptoms have a good outlook: 89.5% of people in the Swedish trial had improved at 6 months after advice on positions, and UK hand surgeons expect mild cases to clear up fully in most people. The NHS says bursitis usually goes away in a few weeks.
Sleep can recover when the cause is treated: in 145 people having surgery for cubital tunnel syndrome, insomnia scores fell from the insomnia range (10.7) to 4.1 within 3 months. No one can promise a timescale.
Sources 26, 27, 21, 25, 12, 13, 28