Abstract: An ultrasonic diagnostic imaging system including a main body housing imaging electronics and a control panel coupled to the imaging electronics comprising: a flat panel display electrically coupled to the imaging electronics; an articulating arm assembly to which the flat panel display is connected for adjusting the viewing position of the flat panel display, the articulating arm assembly including a first lower arm movably mounted to the main body or to the control panel and a second upper arm movably connected to the first lower arm and to the flat panel display, wherein at least one of the arms includes a 4-bar linkage; and a locking mechanism which acts to restrict motion of the articulating arm assembly, characterised in that the locking mechanism comprises a protrusion and a lever having a corresponding seat for engagement of the protrusion, the lever being hinged on one of the two arms to pivot from a rest position to a lock position, the protrusion being correspondingly located on the other arm or