Goniometers, Potentiometers and Electrogoniometers

Potentiometers measure the change in linear or angular displacement by recording the change in voltage output. The potentiometer is positioned over a joint centre of rotation, with each arm orientated along the long axis of the proximal and distal segments. Changes in the angle of the joint will cause the voltage output of the device to change proportionally to the change in joint angle. Angular displacement potentiometers allow movement about one plane to be measured, and potentiometers are typically employed to measure sag-ittal plane movement only. Potentiometers are gener-ally a robust 'student proof' and low-cost method of collecting kinematic data, which can allow real-time  data to be observed. However, they are suitable only they for hinge joins and, if more than one joint is being can assessed at one time, then they may encumber the king movement slightly, thus reducing the validity of the data being acquired. One example of potentiometer is produced by MIE (Leeds, UK)

Electrogoniometers are very thin pieces of wire which are sensitive to bending. The amount of bending ltage changes the output voltage. These can be sensitive to joint angular movement in up to three planes simultane-the ously, although biaxial and uniaxial electrogoniome-nges ters are more common (biaxial referring to the measure rtput of flexion—extension and abduction—adduction of a  joint simultaneously). These are relatively inexpensive, accurate and reasonably unintrusive and so minimize and any gait modification.