MRI examinations of lumbosacral region during eleven years were included to determine frequency of imaging similarity between an extruded discal fragment and a conjoint root. In 7,117 studies included in our casuistic we detected conjoint root in 175 (2.4 %), resembling an extruded discal fragment which is usually well shown by MRI but in our observations corresponded to a conjoint root. Bibliography related with conjoint root was reviewed. Our conclusion support that MRI is the method of choice to differentiate a conjoint root from an extruded discal fragment.