We have compared the sonographic findings of six femoral fractures with soft-tissue interposition which required open reduction with those of a control group of 40 other femoral fractures. Ultrasound assessment before operation showed that the fractured end of the proximal fragment had penetrated the quadriceps muscle anteriorly while the distal fragment lay beneath it. Transverse scans showed less soft-tissue thickness over the end of the proximal fragment in the problem cases. Radiographic image intensification did not provide any additional information. Ultrasound is of value in demonstrating soft-tissue interposition at the fracture site before femoral nailing.