The child with a limp: a case-based approach

The case

A four-year-old is brought to a GP because she has been limping since the morning and does not want to walk on her right leg. She had a cold last week but seems otherwise cheerful, is eating, and has no temperature that her parents have noticed. They wonder whether she has simply twisted something while playing. A limp in a young child always deserves a careful look, because children are not always able to say where it hurts, and the range of causes runs from a harmless irritable hip to a joint infection that is a surgical emergency. The clinician's job is to sort the minor from the serious safely.

Why septic arthritis comes first

The most important condition not to miss is septic arthritis — an infection inside a joint. It is a medical emergency because pus in a joint can permanently damage the growing bone and cartilage within days, and the infection can spread. The classic picture is a child who is unwell with a fever, refuses to move or bear weight on the limb, and holds the joint still because any movement is very painful. Bone infection (osteomyelitis) is a close relative. Because the consequences of delay are so serious, UK practice is to actively consider joint infection in any limping or non-weight-bearing child, and to arrange urgent hospital assessment when the features fit.

The common and the age clues

Most limps are not sinister. In young children a very common cause is "irritable hip" (transient synovitis), a short-lived, self-settling hip inflammation that often follows a viral illness — the child is usually well and afebrile. Age gives useful clues: in toddlers, think minor injury, irritable hip or a subtle fracture; in older children, conditions affecting the growing hip joint become more likely; and at any age, infection must be considered. Other causes include minor sprains, a foreign body in the foot, reactive joint pain after a virus, and, rarely, inflammatory arthritis or a bone tumour. Matching the pattern to the child's age helps focus the assessment.

How the assessment works

The clinician measures the temperature and watches the child walk if they can. They examine the whole limb from hip to foot, looking for swelling, redness, warmth, tenderness and how far the joint will move without distress — often comparing both sides. They gently check the joint above and below the painful area, because hip problems can show as knee pain. A history of fever, how unwell the child seems, recent illness, injury and whether the child will bear weight all guide the next step. When infection is a possibility, urgent hospital assessment with blood tests and an ultrasound or other imaging is arranged, because these help tell a joint infection from a harmless irritable hip.

Red flags and safe follow-up

Several features mean a child should be seen urgently: a fever alongside the limp, refusing to walk or bear any weight, a hot, swollen or red joint, severe pain, looking generally unwell, a limp in a child under three, or a limp that is getting worse or not improving. Night pain, weight loss or a limp lasting more than a week also need review. Even when things look minor, safety-netting matters: parents are told exactly what warning signs to watch for and when to return. A limp that seemed harmless but is joined by fever or worsening pain should always be reassessed rather than watched at home.