Iliotibial band (ITB) syndrome (ITBS) affects 7-14% of runners, 1 2 although it is associated with a variety of activities including cycling, field sports, hockey, rowing, swimming, hiking, and basketball.1 The pain or tightness typically affects the lateral knee but can radiate along the length of the ITB, presenting with hip or thigh pain (fig 1). ITBS is usually caused by biomechanical abnormalities, often combined with overtraining, although it can develop with quite modest levels of exercise. This article outlines how to diagnose ITBS in someone presenting with lateral knee pain, and offers a practical guide to initial management in primary care.