What it is
The Achilles tendon attaches to the back of the heel bone, close to a growth area called the calcaneal apophysis. Repeated running and jumping strain it and it becomes sore, which doctors call calcaneal apophysitis. It is the commonest cause of heel pain in children aged about 8 to 15.
Despite the name, it's an overuse injury rather than an illness. A children's hospital fact sheet calls it a small injury where the calf tendon attaches to the heel bone, sport is unlikely to cause any permanent damage, and children recover completely with no long-term problems.
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What's normal growthEmerging evidence
The heel's growth area appears between about 6 and 12 in girls and 8 and 14 in boys, and fast growth in these years is thought to be part of why heel pain appears then. On MRI (magnetic resonance imaging) scans of 164 children, the growth area began to fuse to the rest of the bone at about 12, and had finished fusing in 78% of 14 and 15 year olds and 88% of 15 to 18 year olds.
A normal growing heel can look abnormal on scans. On MRI, the growth area showed bright patches in 30% of children and lines that can be mistaken for a fracture. On X-rays, it normally looks dense and in pieces, and those features can't make the diagnosis.
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What's normal for Sever's disease, and what isn't
Normal for it: heel pain during or after sport, especially running and jumping, that eases with rest; usually no pain in the morning or after rest; one or both heels (both in 61% of 85 children in an older series); pain when the heel is squeezed; sometimes a limp or walking on tiptoe because of the pain; and a flare in growth spurts.
Growing pains are different: an aching or throbbing in both legs, usually in the evening or at night and gone by the morning, in children aged 3 to 12. They're more common in active children, but they aren't felt in one heel during sport.
Not normal for it: pain at night or first thing, pain in one joint, a limp that carries on away from sport, a hot, red or swollen heel, a high temperature, unusual tiredness, weight loss, or a lump. The NHS asks parents to see a GP for these, and the warning signs at the top of this page give the details.
Sources 2, 1, 8, 9, 10, 11
Who gets it
In Dutch general practice records, 3.7 of every 1,000 registered children aged 6 to 17 had been diagnosed with it. It is more common in boys, who made up 73% of children in the trials, and in children who do frequent high-impact sport such as football, basketball and athletics, or who specialise early in one sport.
A study of risk factors found no evidence that weight or activity level are risk factors, but children in an Australian trial were heavier and taller than average, and older children and those who had had pain longer reported worse pain. Tight calves are often blamed, but a Cochrane review notes that the idea that the shin bone grows faster than the calf muscles can lengthen is unlikely, on current research.
Sources 12, 13, 4, 1, 14, 15
How it's recognisedEmerging evidence
From the story and a heel squeeze. Children's physiotherapists and a children's hospital say X-rays and scans are usually only needed to rule out something else. In 61 children, routine X-rays changed the diagnosis only once (a non-cancerous bone cyst), and surgeons couldn't reliably pick out Sever's disease from X-rays alone. A US series that found other problems (bone cysts, a non-cancerous tumour and stress fractures) in 5% of 98 children argued for an X-ray, so a doctor may want one if the pain doesn't fit the usual pattern.
Sources 1, 3, 4, 6, 7, 16
How long it lasts
Most children get better over time. Children's physiotherapists say the pain usually goes within a few months, though some symptoms last 12 to 24 months; a children's hospital says 6 to 12 months, sometimes up to 2 years. It can come back with the next growth spurt and stops once growth ends. In the Australian trial, children had already had pain for about 9 to 12 months on average. Parents tend to rate its impact as worse than their children do at first.
Sources 4, 1, 3, 2, 17