Hatanaka H, et al. - In this investigation, researchers evaluated the differences between the symptomatic and asymptomatic pre-collapse stage of osteonecrosis of the femoral head (ONFH) in magnetic resonance (MR) findings. Based on plain radiographic findings they examined 123 consecutive hips in 91 patients in the pre-collapse stage of ONFH. According to findings, symptomatic pre-collapse ONFH diagnosed based on plain radiographic findings could be distinguished from asymptomatic pre-collapse ONFH by the presence of bone marrow edema (BME) on MR imaging, and BME can, therefore, be a sign of occult fracture.