Common, usually mild, and mostly short-livedEmerging evidence
In 482 medical students in Jordan, 34% had ever had thumb pain, aches or discomfort while using a phone, mostly at the base of the thumb; 64% of them called it slightly uncomfortable, and 68% said it didn't get in the way of anything. Across 18 studies of university students, 19.2% to 68.7% reported wrist, hand or thumb pain, and in a Canadian university, right hand pain was most common at the base of the thumb, linked with time spent browsing.
These are surveys, mostly of students, and they show links, not cause and effect: a review of 15 studies found the link with hours of use inconsistent, and a review of 42 studies found the evidence for named hand conditions mostly cross-sectional or case reports. In 7,092 young Swedish adults followed for 5 years, texting predicted new hand and finger symptoms a year later (about double the odds) but not five years later, which the authors read as "mostly short-term effects".
In 477 Turkish students followed for 6 months, those whose addictive phone use eased had less pain, and early tendon changes on ultrasound went back. That is one observational study, read as an abstract, not a trial of cutting down. A clinic series of 70 people with hand and forearm pain after heavy device use reported that all recovered with rehabilitation, though it had no comparison group.
Sources 1, 2, 3, 4, 5, 6, 7, 8, 9
Why one thumb does too much: small lab studiesEmerging evidence
Most people hold the phone in one hand and work it with that thumb: in 213 students who held their phones for about 4.9 hours a day, 41% held it in the right hand only with that thumb on the screen, and more than a quarter had discomfort around the right thumb, linked with how long they held the phone that way.
In lab studies, one-handed use made the thumb muscles and the upper trapezius work harder than two-handed use, and one-thumbed texting worked the forearm muscles harder than two thumbs. Keys near the base of the thumb bent it the most and were tapped worst, small targets tired the thumb sooner, and a two-handed grip was faster and steadier with a straighter thumb. Young adults with symptoms moved the thumb faster with fewer pauses. These are small studies of muscle activity and performance in people without pain, often with older keypad phones; none measured whether a change prevents pain.
Sources 4, 10, 11, 12, 13, 14, 15, 16, 17
Where it hurts is the best clueStrong evidence
The NHS sorts thumb pain by its pattern: pain, swelling and stiffness at the base of the thumb that lasts a long time can be De Quervain's or arthritis; pain at the base on the palm side with clicking, a trigger thumb; aching that's worse at night with numbness or pins and needles, carpal tunnel syndrome. It asks you not to worry if you're not sure, and to see a GP if it isn't better in 2 weeks.
De Quervain's is irritation of two thumb tendons in a tunnel on the thumb side of the wrist. US orthopaedic surgeons say it "can be worsened by movements of the wrist and thumb (e.g., typing, texting, or lifting)", and UK hand surgeons say there is little evidence it is caused by work, though hand use aggravates it. Surveys of young phone users found a positive Finkelstein test, a screening test that stretches those tendons, in 19% to 53%, rising with hours of use; but a positive test isn't a diagnosis. Diagnosed De Quervain's is far rarer: 2.8 per 1,000 women and 0.6 per 1,000 men a year in a large US study. The "texting tenosynovitis" label rests on case reports, such as one woman who recovered fully with an anti-inflammatory, splints and less texting.
Sources 18, 19, 20, 21, 22, 23, 24, 25, 26
Phones haven't been shown to cause arthritis or carpal tunnel syndromeEmerging evidence
No study has linked phone use to thumb base arthritis. On X-rays it rises with age and is commoner in women: 5.8% of men and 7.3% of women at 50, 33.1% and 39.0% at 80. In 3,595 Finnish adults, a history of heavy physical work wasn't linked with it. Phone use can make an arthritic thumb ache: in one French clinic, 40% to 45% of people with hand osteoarthritis found phone use painful or uncomfortable, though this wasn't linked with damage on their X-rays.
A trigger thumb is more likely over 40 and with diabetes or rheumatoid arthritis, the NHS says. In Japanese adults aged 50 to 89, 9.7% had had trigger fingers or thumbs, linked with age and being a woman, and hard manual work wasn't a risk factor; only 1 of 42 studies of phone use reported it.
Heavy users had a slightly larger median nerve in the dominant hand on ultrasound, and the nerve changed shape most with the wrist bent sideways, but a review found "no correlation between the number of hours spent using a handheld device and development of carpal tunnel syndrome". A bigger nerve on a scan isn't the condition. Carpal tunnel syndrome causes an ache, numbness, tingling or pins and needles in the hand and fingers, usually worse at night, sometimes with a weak thumb, and needs checking.
Sources 27, 28, 29, 30, 31, 6, 32, 33, 34, 35
When it isn't the phoneStrong evidence
A fall onto the hand or a dropped load can sprain or break the thumb; the NHS lists severe pain, a snap at the time, a thumb you can't move, or a change of shape or colour as signs of a broken thumb. A very high temperature with redness or heat around the thumb can be an infection, NHS inform says, and a hot, swollen joint needs same-day care. Several swollen, stiff finger joints, with long morning stiffness, can be rheumatoid arthritis, which NICE asks GPs to refer urgently. Rarely, a lump. The warning signs cover them.
Sources 36, 18, 37, 38, 51
When a test helps, and how it usually goesStrong evidence
For an ache from using the phone, no scan or test is needed. A clinician tells De Quervain's from arthritis by examining the thumb, including the Finkelstein test. A nerve conduction test or an ultrasound scan is for possible carpal tunnel syndrome when the diagnosis isn't clear, the NHS says, and an X-ray is for an injury.
NHS inform says new hand and thumb problems should begin to settle within 6 weeks in many cases, and the NHS says see a GP if thumb pain hasn't improved after 2 weeks of treating it at home. Diagnosed De Quervain's usually settles with treatment: in a small trial, most people's symptoms had gone at 6 months, and UK hand surgeons say an injection relieves the pain in about 70%. No one can promise a timescale.
Sources 20, 35, 36, 18, 39, 21
