MANY children will experience the aching, cramping or throbbing sensation of growing pains at some point between the ages of three and 12.
While sometimes agonising, this kind of discomfort is thankfully harmless and usually gets better on its own.
However, the pain could be masking something much more sinister.
Conditions like arthritis, transient synovitis, and even cancer can present in similar ways, but be serious and, at times, deadly.
Dr Philippa Kaye, an NHS GP, said: "Growing pains are usually harmless and go away without treatment.
"But, it is important to check that there is nothing else going on."
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What are growing pains?
"Growing pains is a term which is used to describe pains in the legs," Dr Kaye said.
"It can occur in children between the ages of about three and 12."
Weirdly, experts reckon it actually has nothing to do with growth spurts.
Instead, growing pains might actually just be aches from playing sport, jumping, climbing, and running.
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"They seem to be commoner in active children," Dr Kaye added.
What do they feel like?
According to Dr Kaye, children generally describe the sensation as "an aching or a throbbing pain in the legs", which comes and goes over time.
"It is generally worse in the evenings or at night time, and has gone away by the morning," she added.
"Importantly, the pain is felt in the muscles and not the joints of the leg."
Are growing pains normal?
In short, yes. At least two in five kids will experience them and the NHS says: "They are not a sign of anything serious."
Southampton Children's Hospital adds: "Although they can be distressing, growing pains do not cause long-term harm."
How can you treat them?
Painkillers like paracetamol can be great at easing the aches, Dr Kaye said.
Gentle massages, light stretches, and a hot water bottle or heat pack on the painful area can also be a great help, according to the NHS.
When are growing pains not normal?
In some cases, growing pains could be hiding a more serious issue.
The possibilities are almost endless, with "all kinds of things" being potential culprits, Dr Kaye said.
But the following are all health conditions that can cause pain in the legs, which can feel very similar to growing pains.
Juvenile arthritis
Arthritis is often associated with older people, but it can also affect kids in the form of juvenile idiopathic arthritis (JIA).
It causes pain and inflammation in one or more areas for at least six weeks.
Symptoms frequently improve as a child gets older, meaning they can lead a normal life.
However, complications can arise, causing slow growth, thinning bones, and problems with the kidneys and heart, according to John Hopkins Medicine.
Restless leg syndrome
Restless leg syndrome, also known as Willis-Ekbom disease, causes an overwhelming irresistible urge to move the legs.
Some children may confuse this with growing pains as it is often felt in the calves and thighs when sitting or lying down.
While generally harmless, RLS can be "very distressing" and "disrupt a person's daily activities", the NHS says.
This in turn can result in depression and anxiety.
Osteomyelitis
Osteomyelitis is a serious and painful bone infection which causes discomfort and swelling in the legs.
If treated early with antibiotics, it usually goes away fairly easily. But it can cause long-term issues if not addressed.
Sometimes surgery is required to drain a build-up of pus in the bone, or if the infection is pressing on the spinal cord.
The most serious complications include bone death and septic arthritis.
Children are more likely to get osteomyelitis after having a respiratory infection or chickenpox.
Transient synovitis
Transient synovitis, also called irritable hip, is common in children.
Inflammation, often due to a viral illness, triggers pain in the hip or leg and often causes a child to limp, Dr Kaye said.
It usually goes away after two weeks and doesn't cause any long-term problems, but some youngsters will have further episodes.
Knock knees
A gap between your ankles when you stand with your knees together is known as knock knees.
It's common in children aged three to six - around the time they might start to experience growing pains.
Most sufferers won't have any other symptoms, but the condition can cause knee or leg pain and subsequently difficulty walking.
Pulled muscle
Most sprains and strains can be treated at home without seeing a GP and will heal within a few weeks.
But ignoring a muscle injury, which can feel similar to growing pains, can cause ruptures and complete tears, potentially developing into permanent damage, according to Integrated Rehabilitation Services.
Cancer
Persistent bone pain that gets worse over time and continues into the night could be a sign of bone cancer.
While likely to be caused by something else, such as growing pains, it is important to see your GP as tumours can spread.
There are around 550 new bone cancer cases in the UK every year, with about 35 occurring in children.
Some 380 people die - around one every day.
Osteosarcoma - the most common form of the disease in children - often starts at the end of long bones where new tissue forms as a young person grows.
Blood clots
Symptoms of a blood clot include throbbing or cramping pain in the leg or arm.
This can be very serious and needs to be treated quickly.
While rare in young, healthy people, they can happen.
When should you see a doctor?
"If your child has leg pain and a high fever, or a non-blanching rash, or is sleepy or unrousable, please seek emergency medical help by calling 999," Dr Kaye said.
"If they have pain which is in one leg only, if the pain is causing a limp or is affecting their ability to function, walk or take part in activities, if the pain is present in the mornings, or there are other symptoms such as weight loss, please seek urgent medical advice."
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The NHS advises parents to take their little ones to see a GP if they:
- Have pain in just one leg
- Have leg pain in the morning or when walking or taking part in activities
- Have leg pain that's bad enough to stop them walking or makes them limp
- Have joint pain, such as in their knees or ankles
- Have a rash, swelling or unusual bruising on the legs
- Feel unusually tired or sleepy a lot of the time
- Do not want to eat or are losing weight
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