A 92-year-old woman with previous total hip replacement presented with sudden onset of atraumatic hip pain and inability to weight bear. In the absence of radiographic signs of fracture, loosening or biochemical evidence of infection a CT scan of the pelvis and hips was performed, which showed psoas thickening. MRI identified two separate collections related to the psoas and greater trochanteric regions. Ultrasound-guided aspiration was performed to rule out infection and demonstrated a haematoma. In contrast to previously reported cases caused by anticoagulant therapy or inherited coagulopathy, this case was secondary to single antiplatelet agent treatment alone. In the increasingly co-morbid ageing population with associated polypharmacy, aspirin is a common primary and secondary prevention treatment. In patients with atraumatic hip pain, spontaneous psoas haematoma due to antiplatelet therapy should be considered and investigated appropriately.

Musculoskeletal pain is a common presentation in primary care. Although septic arthritis is a rare cause of joint pain, expeditious diagnosis and treatment is of paramount importance to avoid the local destruction of intra-articular cartilage and sepsis. In this article risk factors, pathology, presentation, referral and treatment of suspected septic arthritis are explained, to help GPs identify and manage this potentially life-threatening condition.