Most side neck pain is the muscles and small jointsStrong evidence
The Chartered Society of Physiotherapy (CSP) says neck pain affects most people in their 30s and 40s and is rarely caused by anything serious, and that the most likely cause is a strain of one of the small joints on the side of the neck, the facet joints. The American Academy of Orthopaedic Surgeons (AAOS) names strains and sprains of the muscles and ligaments as the commonest causes.
The NHS lists sleeping in an awkward position, sitting at a desk for a long time, a pinched nerve and injuries such as whiplash (a page past its review date), and NHS inform adds muscle strain or tension, repeating the same strained movements, anxiety and depression, and age-related changes in the neck.
Sources 1, 2, 3, 4
The facet joints in pain clinicsEmerging evidence
In a US pain clinic, the facet joints were the source of the pain in 55% of 500 people with long-lasting neck pain, and in another pain clinic, tenderness when the examiner pressed a single level picked up 94% of facet joint pain. These were people referred for injections, so the figures show what the joints can do rather than how often they cause everyday neck pain.
Sources 5, 6
Lifestyle matters more than postureEmerging evidence
The CSP says poor sleep, muscle tension, low activity and stressful periods can all make the neck more sensitive, and that posture plays a much smaller role than people think; long spells in one position seem to matter more. High blood pressure, which people often blame, doesn't usually cause any symptoms, the NHS says.
Sources 1, 7
Swollen glandsStrong evidence
Swollen glands feel like tender, painful lumps on each side of the neck or under the chin. The NHS says they are usually a sign of the body fighting an infection, such as a cold, tonsillitis or an ear or throat infection, and go down within 1 to 2 weeks; glandular fever, most common at 15 to 24, causes swollen glands with a high temperature, a sore throat and extreme tiredness, and gets better within 2 to 4 weeks.
A US review says about 1 in 100 unexplained swollen glands seen in general practice turns out to be cancer, more often from age 40 (4%) than younger (0.4%).
Sources 8, 9, 10, 11, 12
A lump isn't always a glandStrong evidence
The NHS lists swollen glands, a goitre (a swollen thyroid) and non-Hodgkin lymphoma among the causes of a swelling in the neck. A thyroid lump sits at the front, low in the neck; most thyroid lumps are harmless and about 10% are cancer, which an ultrasound scan and a needle sample assess, a review says, and the British Thyroid Foundation advises seeing your doctor with a minimum of delay about any lump or swelling. The commonest symptom of lymphoma is a painless lump in the neck, armpit or groin.
A salivary gland stone causes pain and swelling in the mouth that flares up, especially at mealtimes, and mumps causes painful swelling of the cheeks and neck. A US guideline says a lump in the neck that persists in an adult should be checked for cancer until shown otherwise.
Sources 13, 14, 15, 16, 17, 18, 19, 20, 21, 22
Rare causes: a painful thyroid and painful swallowingEmerging evidence
A painful, tender, swollen thyroid that comes on over 24 to 48 hours, often with a sore throat or a flu-like illness, is usually viral (subacute) thyroiditis, the British Thyroid Foundation says; it can make you jittery with a racing heart for a while, and most people recover completely in 2 to 5 months. It is rare: about 5 people per 100,000 a year in one Minnesota population.
Rarer still, calcium in a deep neck muscle tendon (longus colli calcific tendinitis) causes neck pain, stiffness and painful swallowing. It settles by itself but can look like an abscess or meningitis, so it needs checking; it is described in a short series of 5 people.
Sources 23, 24, 25, 26
The emergencies: meningitis, a bleed and a torn arteryStrong evidence
The NHS says call 999 for possible meningitis: a stiff neck and not being able to look at bright lights, a very painful headache, a very high or very low temperature, confusion, a rash that doesn't fade, or a first seizure. A bleed on the brain (subarachnoid haemorrhage) causes an extremely painful headache that starts suddenly, with neck pain or stiffness. Stroke signs that pass within minutes still need a 999 call.
A tear in a neck artery (a dissection) is rare, about 2.6 people per 100,000 a year in a Minnesota population, but head or neck pain was its commonest first symptom, in about 80%. In a study of 279 people, the pain was often a pulling pain, new in character for 75% of those who already had headaches, and a review notes it can mimic an ordinary headache. It can lead to a stroke, which is why head or neck pain unlike any before, especially with dizziness, vision or speech problems or a weak arm, is a 999 call. Most people recover well: 92% had a good outcome in the population study.
Sources 27, 28, 29, 30, 31, 32, 33
When a scan or test helpsStrong evidence
For ordinary side neck pain, no scan is needed: the CSP says there is not a strong link between X-ray or magnetic resonance imaging (MRI) findings of wear and tear and a person's pain, and X-rays are generally not needed for a wry neck. After a neck injury, a rule from the National Institute for Health and Care Excellence (NICE) decides: someone at low risk who is pain-free and can turn their head 45 degrees each way needs no imaging, while being 65 or over, a dangerous fall or crash, or tingling in the arms or legs means imaging.
A lump is examined, and if needed checked with an ultrasound scan or a small sample (a biopsy); thyroid lumps are checked with an ultrasound and a fine-needle sample. A review says a single swollen gland that looks unlikely to be cancer can be watched for 4 weeks. From age 40, NICE asks GPs to consider an urgent chest X-ray for swollen glands above the collarbone, or glands in the neck that don't go away.
Sources 1, 34, 35, 13, 16, 12, 36
How it usually goesEmerging evidence
The NHS says most neck pain only lasts a few weeks; NHS inform says the biggest change comes in the first couple of weeks and most problems improve within 8 weeks; and the CSP says most first episodes get a lot better within three months, though about half of people have it again at some point. An acute wry neck usually improves within 24 to 48 hours, sometimes up to a week.
Swollen glands from an infection go down within 1 to 2 weeks, a sore throat usually gets better within a week, tonsillitis within 3 to 4 days, and glandular fever within 2 to 4 weeks. Subacute thyroiditis settles over 2 to 5 months. No one can promise a date.
Sources 3, 4, 37, 1, 34, 8, 10, 9, 11, 23