A 4 year old boy attended the emergency department with a two week history of “limping.” On further questioning he also had vague left sided pain in the knee and thigh. He was otherwise well, with no constitutional symptoms and no history of injury. On examination he was afebrile. He was reluctant to put weight on the affected leg, hurrying quickly off it when walking. Knee movements were unremarkable, but he had marked restriction of internal rotation and abduction of the left hip. Blood results showed a haemoglobin of 130 g/L (reference range 100-148), white blood cell count of 9×109 cells/L (6.3-16.2), C reactive protein of 5 mg/L (0-8), and erythrocyte sedimentation rate of 12 mm/h (2-8). Given the duration of symptoms radiography was performed. The findings were thought to be inconclusive (fig 1⇓), so pelvic magnetic resonance imaging (MRI) was performed (fig 2⇓). Fig 1 Plain anteroposterior radiograph of the pelvis Fig 2 T2 weighted coronal magnetic resonance imaging scan of the pelvis ### 1 What is the name for this gait pattern? #### Short answer A limp caused by a shortened stance phase in the gait cycle is known as an antalgic gait. #### Long answer A limp is an abnormal gait pattern commonly caused by pain, weakness, or deformity. The term is generally used to describe a shortened “stance phase” in the gait cycle, with the person “hurrying” off one leg to offload a …