A goniometer may be any device that measures the angle between two lines. A medical goniometer specifically measures the angle of a joint's range of motion. Medical professionals commonly use goniometers to evaluate the injury to a joint or to monitor the joint's improvement during rehabilitation.
Measurement
A goniometer typically measures angles in units of degrees. A complete circle contains 360 degrees. You may also refer to a 90-degree angle as a right angle. You may also call a 180-degree angle a straight line.
Construction
A goniometer generally consists of two arms joined by a circular portion. The circular portion contains a hole in the center which allows you to place the center of the goniometer over a desired point. A meter on the central portion of the goniometer measures the angle separating its two arms.
Operation
Place the central hole above the center of the joint while the joint is in the desired position. Align each arm of the goniometer along one of the limbs that the joint moves. Read the goniometer to obtain the angle between the two limbs.
Procedure
A joint's range of motion will be the difference in the angular measure between a joint's fully extended position and its fully flexed position. For example, the fully extended position for the elbow occurs when the upper and lower arms are as close to a straight line as is comfortable. The fully flexed position for the elbow occurs when the lower arm is as close to the upper arm as is comfortable.
Evaluation
Compare your joint's range of motion to a standard value. For example, the normal angle for a fully extended elbow is 180 degrees and the normal angle of a fully flexed elbow is about 40 degrees. The normal range of motion for the elbow, therefore, is about 140 degrees.
