Methods and apparatus for treating a patient (14). The method includes acquiring a plurality of radio frequency (RF) signals (90) with an ultrasound transducer (24), each RF signal (90) representing one or more return echoes (64) from a scan line of a pulse-mode echo ultrasound scan. A position of the ultrasound transducer (24) corresponding to each of the acquired RF signals (90) is determined, and a plurality of contour lines (156) generated from the plurality of RF signals (90). The method estimates a 3-D shape and position of an anatomical feature, such as a joint (12) of patient (14) based on the generated contour lines (156) and corresponding ultrasound transducer positions. An apparatus, or computer (36) includes a processor (42) and a memory (44) with instructions that, when executed by the processor (42), perform the aforementioned method.
