Limp is a symptom and not a diagnosis
There are red flag conditions not to be missed which can occur at all ages. The causes of limp can be broadly divided into acute and chronic and categorised by age.
Common pitfalls in making a diagnosis of limp include:
- Ascribing limp to trauma and overlooking features that suggest other causes.
- Referred pain (e.g. from the abdomen (and testes in boys), back or chest and hip pathology manifesting as knee pain).
- Think beyond the hip (!) and examine the child comprehensively.
- Assess for proximal muscle weakness; ask the child to get up from the floor (Gowers’ manoeuvre), jump or climb a step
- Classical clinical features of sepsis may be masked in the immunosuppressed child.
- Mycobacterial infection can be easily missed.
- Synovial fluid may be sterile in partially treated septic arthritis.
- Labelling children with daytime symptoms as having “growing pains”.
- Medically unexplained limp or physical symptoms warrant specific management and referral (i.e. discharge without a diagnosis and follow up plan is not advised).
- The blood film may be normal in children with malignancy.
- Radiographs are often normal in children with early sepsis or arthritis.
- Acute phase reactants may be normal in children with arthritis.
- Rheumatoid factor is usually negative in children with arthritis.
- Antinuclear antibody and rheumatoid factors may be false positives in children without inflammatory joint or muscle disease.