Background

Septic arthritis refers to infection of a joint. It can occur in several different patient groups: in adults post-joint replacement, post-traumatically or spontaneously, especially in diabetics. Another important patient group is the limping child with a septic hip (see discussion in Chapter 59, ‘Perthes’ disease’).

It is important to make the diagnosis as early as possible. Patients may become very ill and delayed or missed diagnosis may lead to destruction of the joint, a particular issue in children.

Clinical features

The condition usually presents as a monoarthritis of sudden onset. It may be caused by septicaemia. Elicit a history of joint replacement or trauma. There may be signs and symptoms of infection – fever, unwellness, joint pain and effusion.

In children – septic arthritis, Perthes’ disease, slipped upper femoral epiphysis (SUFE) and irritable hip need to be differentiated. Always think of infection, which can occur at any age. Irritable hip is a diagnosis of exclusion and other possible causes must be excluded before this diagnosis is made.

Age is the key discriminator. SUFE most commonly occurs in 10–16-year-olds (see Chapter 58) and Perthes’ disease in children aged 5–12 (see Chapter 59). These patients are usually systemically well. Irritable hip occurs in children aged 3–10. There is usually a preceding or concomitant viral illness. Systemic pyrexia is unusual.

One study [1] demonstrated that paediatric patients who were non-weight-bearing, with erythrocyte sedimentation rate (ESR) > 40, white cell count >12 × 10⁹/L and fever almost always had septic arthritis.