Why use a goniometer when you can use the accugoniometer and have less margin of error with your measurements. The accugoniometers levels present on the arm, aid in acquiring accurate ROM measures with External and Internal Rotation. These measurements are one of the more important planes of motion we should be measuring. Without the accugoniometers levels,  the clinician has rely heavily thier visual field to acquire that 0 deg angle from the fulcrum.  The standard of error with external/internal rotations tend to be higher than the standard of error of 4 deg we have learned from research. New studies are showing these measurements tend to be upwards of 8-10 deg of error. This error can play a huge factor in figuring out if a particular intervention was actually efficacious or not. The accugoniometer will resolve this greater error and get it back down to the normal standard in which we are accustomed to.