What growing pains areStrong evidence
The NHS describes growing pains as leg pain that is common in children aged 3 to 12, harmless and usually gets better on its own: an aching or throbbing in both legs, in the evening or at night, gone by the morning, coming and going over months or even years.
Reviews add the details. The pain is usually in the shins, calves, thighs or behind the knees rather than in the joints; it can wake a child; it lasts minutes to hours; there's no swelling, redness or tenderness; and the child is well, runs about normally the next day and has a normal examination. Doctors also call them benign nocturnal limb pains of childhood: harmless night-time pains in the limbs.
Sources 1, 2, 3, 4, 5, 6
How common they areEmerging evidence
In a random sample of 1,445 Australian children aged 4 to 6, 37% had growing pains. In 777 Danish preschool children followed with text messages every 2 weeks, 24% to 43% had them, depending on the definition. Older estimates range from 2.6% to 49%, largely because definitions differ: a review of 145 studies found very poor agreement on what counts, and another review counted 15 different sets of diagnostic criteria.
Sources 7, 8, 4, 9, 10
What the pattern looks like
In the Danish children with growing pains, episodes came 1 to 3 times a week in 80%, started in the late afternoon or evening in 62% (at night in 20%, in the day in 14%), and 80% had pain in both legs. About a quarter had disturbed sleep, but 56% had no other effects. In one series of 44 children, 43% had episodes at least once a week.
One leg can ache more than the other at times, but the NHS lists pain in 1 leg among the reasons to see a GP, so it can be checked.
Sources 8, 2, 5, 1
They aren't caused by growingStrong evidence
The NHS says growing pains are not caused by growing and are not a sign of anything serious. The peak age, around 6, isn't a time of fast growth, and the Danish study found no link with periods of rapid growth.
Sources 1, 2, 8
What might cause them, and where the sources disagreeMixed evidence
Nobody knows the cause. On activity, the sources point in different directions. The NHS says growing pains are more common in active children and can happen after playing lots of sport, and NHS and children's hospital leaflets link them with busy, active days. But an Australian health service says children who do lots of exercise don't often get them, and in a 2026 study of 290 children with growing pains and 467 without, a preference for sport went with fewer growing pains, while extreme tiredness after exercise went with more. A 2026 review grouped very flexible joints and physical activity together as one risk factor. So it isn't known whether activity makes them more or less likely.
Other ideas have some evidence:
- Very flexible joints: the NHS says growing pains are common in children with joint hypermobility syndrome, which usually affects children and young people, often gets better with age, and is treated mainly by building muscle strength and fitness.
- A lower pain threshold: in a study reported in a review, children with growing pains felt pressure as pain sooner, and in a 5-year follow-up, those whose pains carried on kept the lower threshold.
- Families and genes: about 70% have a parent, brother or sister who had them, and identical twins are far more alike than non-identical twins (concordance 0.85 against 0.36).
- An overlap with restless legs: in a twin family study, about a third of cases also had features of restless legs syndrome, an urge to move the legs. Growing pains as a whole were linked with low iron, but not once those cases were set apart. The NHS links restless legs with iron levels.
Sources 1, 11, 6, 12, 13, 14, 15, 16, 2, 17, 4, 18, 19, 20, 21
How long they lastEmerging evidence
Months to years, coming and going, and they usually stop by the mid-teens, though some young people still get them in their early teens. Of 35 children followed for 5 years, 51% had stopped and 83% of the rest had milder, less frequent episodes. None developed fibromyalgia, a long-term widespread pain condition.
Sources 1, 2, 13, 17
Hip problems that can show up as thigh or knee painStrong evidence
The NHS says hip problems in children can sometimes be felt in the thigh or knee, and that sudden pain in the hip, thigh or knee, or a limp, needs an urgent GP appointment or NHS 111. Irritable hip is the commonest cause of hip pain in children and usually settles in 1 to 2 weeks, but it should always be checked. Two rarer conditions matter because early treatment helps:
- Perthes disease: the blood supply to the ball of the hip is disrupted and the bone softens, then regrows over 2 to 5 years. It usually starts between 4 and 10, is much commoner in boys, and affects both hips in about 10% to 15%. A limp, often painless, usually comes first, with pain in the hip or groin that can spread to the thigh or knee; in some children knee pain is the first symptom. In the UK it starts in about 2.5 in 100,000 children aged up to 14 each year.
- A slipped growth plate at the hip (slipped upper femoral epiphysis, or SUFE): the ball at the top of the thigh bone slips at its growth plate around puberty, most often in boys aged 12 to 16 and girls aged 10 to 14, and more often in children who are overweight. It causes weeks or months of groin, hip, thigh or knee pain that's worse with activity, a limp, and a leg that turns out or looks shorter. It needs an operation, usually a screw, and acting fast prevents further slipping. In the UK it starts in about 3 in 100,000 children aged 6 to 18 each year. In a national study of 486 children, 344 had waited more than a week from their first symptoms to treatment, and in 96 of 311 accounts of the delay, the child had been seen more than once with a first diagnosis such as a groin sprain or growing pains.
Sources 22, 23, 24, 25, 26, 27, 28
Other things a GP will want to rule outStrong evidence
A bone infection causes pain, swelling, warmth and redness over a bone, a limp and usually a high temperature, though young children don't always get a temperature. A joint infection causes sudden severe pain in one joint, swelling and difficulty moving it or putting weight on it. Arthritis in children shows as a swollen, stiff joint, and the NHS lists pain in 1 joint and swelling among the reasons to see a GP.
Leukaemia and bone tumours are rare. Warning signs include bone or joint pain with tiredness, looking pale, bruising or bleeding easily, fevers, getting ill a lot, swollen glands or weight loss, and bone pain that is worse at night, or a lump. NICE asks GPs to arrange a very urgent blood count for a child with persistent or unexplained bone pain, and to consider a very urgent X-ray for unexplained bone pain or swelling.
To keep this in proportion: about 1 in 3 young children get growing pains, while Perthes disease and a slipped growth plate each start in about 3 in 100,000 children a year. The warning signs exist because the rare causes need early treatment.
Sources 29, 30, 1, 31, 32, 33
