1. A computer system, comprising: a processor; and a program storage device readable by the computer system, embodying a program of instructions executable by the processor to perform method steps for automatically detecting and registering bone structures from magnetic resonance imaging (MRI) images, the method comprising: acquiring an MRI image; automatically detecting low or zero intensity locations within the image and extracting a bone border based upon the detected low or zero intensity locations; segmenting a region of the image within the extracted bone border; building a model of a bone using the extracted bone border and the segmented image region by extracting geometric primitives from the detected bone borders; and registering the extracted bone border to the model.