A limp that came out of nowhere

Why this one does not get watched overnight

The AAP's symptom guidance is unusually direct here. Walking that is not normal — a new limp — sits on the list of reasons to call the doctor or seek care now, and to be seen within twenty-four hours. A child who cannot stand or walk at all is on the go-to-the-emergency-room-now list.

That is not because a limp is usually sinister. It is because the examination is what separates the causes, and several of them get materially worse with delay.

Small children also localise pain badly and under-report it. A child who is limping but insists nothing hurts is still limping, and the limp is the finding.

The common one, which is temporary

Most sudden limps in this age group turn out to be transient synovitis — KidsHealth calls it toxic synovitis — a temporary inflammation of the hip that causes limping and pain in the hip and leg.

It is most common in children between three and eight years old, and more common in boys. Many children develop it after a viral infection such as a cold or diarrhea, which is why the story is so often a limp appearing a few days after a bug that seemed to be resolving.

The pain usually comes on suddenly and on one side. Children may limp with the leg held oddly, walk on tiptoes, or complain after a long rest, and younger children may refuse to walk or simply cry. It usually goes away within a week or two, though it can sometimes last four to five weeks.

Encouragingly, KidsHealth notes children can usually walk comfortably again within a day or two of starting anti-inflammatory medicine — but that is a treatment decision for the doctor who has examined them, not one to make at home.

When they point at the knee, look at the hip

This is the single most useful thing to know here, and it catches out parents and occasionally clinicians.

Hip problems in children very often present as knee or thigh pain. KidsHealth lists knee or thigh pain among the symptoms of a hip inflammation. The child is not confused and not exaggerating — that is genuinely where they feel it.

So a child limping and complaining about their knee should not have the hip dismissed, and if a doctor examines the hip when your child said knee, that is the right move rather than a misunderstanding.

The combinations that mean now

Fever plus pain in one leg only is the one to memorise. The AAP lists it as a reason to be seen immediately, and it is the overlap where the benign explanation and the dangerous one look most alike.

Septic arthritis is a bacterial infection inside a joint. The AAP describes it as a medical emergency, with severe joint pain, joint stiffness and a high fever. A child who will not let you move a joint at all — not guarding it, genuinely resisting any movement — belongs in this picture.

A bone infection behaves similarly. KidsHealth's description of how it shows in the youngest children is worth carrying: very young children might stop using the infected limb and protect it from being touched, and may be fussy or eat less. Their instruction is that a child with a fever and bone pain should visit the doctor right away, because it can get worse within hours or days and become much harder to treat.

Severe pain when the leg is touched or moved, or a child too weak to stand, are on the AAP's emergency lists in their own right.

This is not growing pains

Growing pains have their own page here, and the distinction matters because the label gets applied far too readily to any leg complaint in a small child.

The pattern that gets called growing pains is night-time leg aching, usually in both legs, in a child who is completely well and walks normally the next morning.

A limp is a different observation entirely. It is one-sided, it is visible, and it happens while they are awake and moving. Whatever is causing it, it is not the thing people mean by growing pains, and it should not be filed there.

What to tell them when you call

When it started, and whether anything preceded it — particularly a cold, a sore throat or a tummy bug in the past couple of weeks, since that is the classic run-up to transient synovitis.

Whether they can bear weight at all, and whether it is getting better, worse, or staying level through the day.

Whether there is a fever, and whether the pain is in one leg only.

Any fall, even a small or unwitnessed one. Small children fall constantly and out of sight, so an absent injury history does not rule one out — say so rather than leaving it out.

Which joint they will not move, if there is one, and whether they resist you moving it.

Go to the emergency room now if

They cannot stand or walk at all, or are too weak to stand.

There is a fever together with pain in one leg only.

They cannot move a hip, knee or ankle normally, or scream when it is moved.

There is severe pain when the leg is touched.

The joint is hot, swollen or red.

They look or act very sick, however unremarkable the leg seems.