The child who presents with fever, limp and hip pain will often undergo multiple diagnostic procedures before a definitive diagnosis is made. We describe a diagnostically challenging case of a 14-year-old boy presenting with an atraumatic painful limp and pyrexia. Eventually the diagnosis of obturator internus muscle abscess with associated ischial osteomyelitis was made. Of the 19 previous cases reported, four children had associated osteomyelitis and were of an older age. Symptomatology varies, clinical examination is non-specific and the diagnosis can be difficult. Haematological indices are more predictive than in cases of classical osteomyelitis or septic arthritis. Subtle features on conventional radiography and isotope bone scanning should not be overlooked while CT and MRI may be complementary in diagnosis.