An electrogoniometer uses angle sensors to objectively measure human joint motion. It has two arms attached to the proximal and distal segments of the joint, connected to a potentiometer that measures the angular position as voltage. This voltage is sampled and converted to an angle. Electrogoniometers include optoelectronic systems using cameras, potentiometers measuring resistance, and strain gauges using flexible springs. They are portable, lightweight, and adapt to different body segments but can interfere with natural movement. Electrogoniometers provide precise dynamic joint angles and are reliable for laboratory studies.

1. ELECTRONIC GONIOMETER
PRESENTED BY – GROUP 3

2. INTRODUCTION
 Electrogoniometry is one of the methods of kinematic
measurements to objectively measure the human motion.
 Electrogoniometers are the electronic devices which uses angle
sensors to measure dynamic movement of the joint.
Components
 These devices have two arms, similar to those of the
universal goniometer, which are attached to the proximal
and distal segments of the joint being measured.
 A potentiometer is connected to the two arms.

3. WORKING OF ELECTROGONIOMETER
POSITIONING
 The arms of the electrogoniometer are strapped to the body segments,
such that the axis of rotation of the goniometer is approximately aligned
with the joint’s axis of rotation.
WORKING
 Rotation of a calibrated potentiometer measures the angular position of
the joint.
The angle of the joint is converted to voltage which is sampled
continuously and again converted to an angle using manufactured
supplied scale factor.
 The related output voltage is typically measured by a computer data
acquisition system (analog to digital data) which display the joint angle
in real time.
 The position data obtained from the electrogoniometer combined with
the time data can be mathematically converted to angular velocity and
acceleration.

6. TYPES OF ELECTOGONIOMETER
 Optoelectronic Systems – These are video systems that use one or more
video cameras to track bright markers placed at various locations on the
patient’s body. These markers are either infrared (IR), light emitting diodes
(LEDs) or solid shapes of reflective tape. The system keeps track of the
vertical and horizontal coordinates of each marker, and computer software
processes this information to determine the angle on the body segments of
interest.
 Optoelectronic systems offer good precision
 But their collaboration procedures and data analysis are time-consuming.

7.  Potentiometers - A potentiometric element is attached to a
joint’s rotation point. The potentiometer’s electrical
resistance can be used to determine the angle between the
joints.
 These types of electrogoniometers are somewhat bulky and
restrict patient’s movement.
 The instrument’s precision can also be compromised due to
inability to follow any changes in the joint’s axis of rotation.
.

8.  Strain gauges – Also known as flexible goniometers, a strain gauge is
flexible spring with plastic end blocks on each end. The strain gauge
mechanism is housed inside the spring, which changes its electrical
resistance proportionally to the change in angle between the plastic end
block’s longitudinal axis.
 Strain gauges are light weight, portable, easily applied
 do not restrict movements not interfere in patient’s activities and adapt well
to different body segments.
These are currently the most popular electrogoniometers.

9. ADVANTAGES
 Ease of use
 Cost effective than other methods of measuring dynamic movements
 Determine precise joint angles which is extremely important in
rehabilitation.
 Angle data is essential for determining abnormal patterns,
characterizing disability, impairments, handicap

10. DISADVANTAGES
 They are less accurate than other systems used to record
movement.
 In addition, both designs i.e. potentiometers and strain
gauge require placement over the joint, which may
interfere with the natural kinematics because of
cumbersome cabling and method of attachment.
 Another drawback of these devices is that while they
provide a relative measure of joint angular position
 The computation of which requires knowledge of the
absolute positions of the body.

11. RELIABILITY OF ELECTROGONIOMETER
 The electrogoniometer evaluated has a very high precision when range of
motion measurements are made.
 A systematic review of measurement tools (standard goniometers,
fluid- and gravity-based inclinometers, photographs, and motion
analysis systems) used to quantify knee joint motion found that for
dynamic measurements, electrogoniometers and 3D motion
analysis systems were the most reliable and had low
measurement error.
 There is a reliability study on the use of universal goniometer and electro
goniometer in measuring knee range of motion which concludes that
Universal goniometer in clinical evaluation (as they are easy to be
employed) and electro goniometers in laboratory studies ( as they are
more accurate) are reliable.

12. References :
o Donald A Neumann, Kinesiology of Musculoskeletal
System: Foundations for rehabilitation.3rd edition.Elsevier
,Inc.;2010
o Leonardo Mangiapelo, Implementing an
electrogoniometer;2008