Where it hurts is a clue, not a diagnosisEmerging evidence
No study we found has counted the causes of pain felt at the back of the shoulder, so this list is pieced together from pain maps, the American Academy of Orthopaedic Surgeons (AAOS) and studies of trapped neck nerves. In pain maps from 94 people, rotator cuff pain sat mostly at the front of the shoulder, spreading down the arm. When the maps were tested in 194 new patients, the place the pain was felt predicted the diagnosis only 45% to 50% of the time.
The AAOS says arthritis of the main shoulder joint is felt in the side or back of the shoulder. A trapped nerve in the neck commonly sends pain to the shoulder blade and the back of the shoulder: in 25 people, the C5 nerve root sent pain above the shoulder blade and C6 from there to the back of the deltoid. NHS inform says neck problems can be felt in the shoulder even without neck pain.
Sources 1, 2, 3, 4, 5
The rotator cuff and the jointEmerging evidence
Subacromial (rotator cuff) pain is the commonest shoulder problem, NHS inform says: pain at the top and outside of the shoulder and in the upper arm, worse lifting the arm above shoulder height or reaching behind your back, and hard to lie on. The cuff muscles at the back, the infraspinatus and teres minor, take high loads when a throwing arm slows down, the AAOS explains.
Most wear-related cuff tears are relatively painless, the AAOS says; tears that hurt cause pain at rest and at night and weakness lifting or turning the arm, and a sudden tear after a fall causes intense pain, a snap and immediate weakness. Arthritis of the joint brings a deep ache, grinding, stiffness and night pain, usually over 60. Frozen shoulder causes pain and stiffness in every direction, worse at night, lasting months to years.
Sources 6, 7, 8, 9, 3, 10
Throwers, pressing and the back of the jointEmerging evidence
In throwers and other overhead athletes, the cuff tendons at the back can be pinched inside the joint during the wind-up (internal impingement), often with a tight back of the shoulder and looseness at the front; the back of the shoulder also takes the load of slowing the arm after release. Tenderness along the back of the joint and lost inward rotation are typical.
The joint can also slip backwards (posterior instability). Reviews say this often causes vague, deep pain without a clear injury, and contact athletes describe pain with push-ups and the bench press. A full backward dislocation is rare, about 1.1 per 100,000 people a year: in one series, 67% followed an injury and most of the rest a seizure, and 17.7% dislocated again within a year.
Sources 8, 11, 12, 13, 14, 15
The neckEmerging evidence
In a review of 86 studies of trapped neck nerves, 72% of the reports described pain over the shoulder blade, which can come weeks before any arm pain. Painful small joints in the neck also send pain over the top of the shoulder and the shoulder blade, in overlapping patterns. Arthritis UK says tingling in the hand or arm with shoulder pain probably comes from the neck.
Clues that it's the neck, from a consensus of 22 physiotherapists: symptoms below the shoulder, past or present neck pain, symptoms that change when you move your neck, and pins and needles or burning. The NHS says neck arthritis (cervical spondylosis) needs an urgent GP appointment with pins and needles in an arm, pain between the shoulder blades, or heaviness or weakness in the arms.
Sources 16, 17, 18, 19, 20, 21
The muscles around the shoulder bladeEmerging evidence
Altered shoulder blade movement (dyskinesis) raised the risk of future shoulder pain by 43% in 419 athletes without symptoms (35% against 25%), and a consensus calls it common in shoulder problems, though its exact role isn't known.
Soreness across the back of the shoulder a day or two after new or harder training, such as rows or reverse flies, is delayed onset muscle soreness: a review found that exercise eases it for a while, stretching and cold don't, and it settles by itself. "Knots" or trigger points can't be found reliably: across 9 studies, examiners often disagreed.
Sources 22, 23, 24, 25
Trapped nerves: uncommon, but worth knowingEmerging evidence
The suprascapular nerve supplies the cuff muscles over the back of the shoulder blade. A review estimates its problems at 1% to 2% of shoulder pain, mostly in people under 40 who play overhead sports or who have a massive cuff tear, and says they're often missed. In volleyball, the wasting is often painless: 12 of 96 top players had it, with about a fifth less outward-turning strength, and among 82 professionals, 9% of men and 12% of women had wasting with weakness but no pain.
Quadrilateral space syndrome, a squeezed nerve and artery in a gap behind the armpit, is rare and a diagnosis of exclusion: vague pain and pins and needles over the outer shoulder and arm, worse with the arm up and turned out, mostly in young overhead athletes. After a hit in contact sport, a burning pain from the shoulder to the hand (a stinger) usually settles within seconds to minutes; weakness lasting more than several days needs checking.
Sources 26, 27, 28, 29, 30, 31, 32
Causes that aren't the shoulderStrong evidence
The heart: chest pain that spreads to the arm, neck, jaw or back, especially with breathlessness, sweating or feeling sick, is a 999 call. The NHS heart attack page names the arms, neck and jaw; its chest pain and angina pages add the back, and the British Heart Foundation names the upper back for women. The lungs: a clot in the lung, and pleurisy, which causes sharp chest pain on breathing in that can spread to the shoulders and back.
Lung cancer can cause chest or shoulder pain, the NHS says, alongside a cough that won't go away, breathlessness or weight loss. A rare tumour at the top of the lung (a Pancoast tumour) causes severe, constant shoulder and arm pain down the inner arm, a droopy eyelid and weak hand muscles. The list of reasons for an urgent chest X-ray from the National Institute for Health and Care Excellence (NICE) doesn't include shoulder pain on its own.
Shingles can start as a burning or tingling patch on one side before the rash; polymyalgia rheumatica causes pain and stiffness in both shoulders over 50; and a hot, swollen shoulder with a fever can be an infection. The AAOS calls tumours, infection and nerve problems much less common causes of shoulder pain.
Sources 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45
Tests and scansEmerging evidence
Most shoulder pain is diagnosed from the story and an examination. A GP may arrange an X-ray to check the cause, and after a suspected dislocation you'll usually have one. Ultrasound or magnetic resonance imaging (MRI) helps when a cuff tear or a labral injury would change treatment, but scans often show cuff changes that aren't causing pain.
Nerve tests and MRI confirm a suprascapular nerve problem, while there's no reliable scan for quadrilateral space syndrome. Arthritis UK says a chest X-ray may be recommended for unexplained shoulder pain lasting more than 3 weeks in a smoker over 40. Chest pain needs an electrocardiogram (ECG) and blood tests in hospital, not a shoulder scan.
Sources 46, 47, 9, 26, 30, 19, 33
How it usually goesEmerging evidence
NHS inform says most shoulder problems start to improve within about 6 weeks, and the NHS says some take 6 months or longer; frozen shoulder takes months to years, and most neck problems improve within 8 weeks. In the GRASP trial, people with rotator cuff pain improved over 12 months whether they had one advice session or more physiotherapy. With the movement-related suprascapular nerve problem, over 80% got pain relief without surgery, and volleyball players with painless wasting mostly kept playing. No one can promise a timescale.
Sources 5, 47, 10, 48, 49, 26, 50, 15
