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by GONIOMETERAbstractBackgroundMethodsResultsConclusion


by EYEAbstractBackgroundMethodsResultsConclusion


Grey, K.:  "Measuring articular range of motion (ROM).  An investigation of accuracy and reproducibility." 1988.





Background: The accuracy of measurement of ROM is often questioned, and in our daily work we experience discrepancies between our observations.

Methods: An investigation of variation during goniometric measurements. Five physiotherapists performed series of measurements (10-20) on two models, a geometric linear angle drawing, the outlines of a flexed knee drawn on paper and the actual knee of one test person.  

Results: Variation is smallest when measuring a geometric drawing (3 grader), and largest when measuring a living test person. In the latter case the smallest median was 135 degrees (therapist #1), and the largest median was 160 degrees (therapist # 2). The largest individual variation was 15 degrees (span: min.-max.).

Conclusion: Measuring of angular ROM requires meticulous care to be exact.  When evaluating  and comparing results only one and the same therapist should perform the measurements to avoid variance.

 When questioned about their daily work, none of the therapists actually used goniometers, but used measurement by eye or other  means of evaluation. Often functional testing was preferred.

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The variation in measurements of ROM is partly due to the therapists, and partly due to the  nature of the measurement.  


5 physiotherapists performed measurements of angles:

Ten-twenty measurements were made on each of three objects:

  1. This object consisted of an angle drawn as two straight lines on a sheet of paper.
  1. The second object was a drawing: the outlines of the thigh, knee and lower leg of the test person were drawn on a sheet of paper with the knee placed at a random angle.
  1. The third set of measurements was carried out on the knee of a test person. The therapists were instructed to measure maximum passive knee flexion with the hip flexed and the test person lying in supine position. 


These measurements were made:

  • Therapist #1 (T1) made 3 x 10 measurements
  • T2 made 2 x 20 measurements
  • T3 made 3 x 15 measurements
  • T4 made 3 x 10 measurements


These four therapists all used the same goniometer, 15 cm long and a scale divided at 5 degrees intervals. The accuracy of the reading would at its best be +/- 1 degree.


  • T5 made 2 x 20 measurements


In this case another goniometer of the Zimmer brand was used, goniometer-legs 25 cm long and with a scale divided at intervals of one degree. The accuracy of the reading was subsequently better: +/- 0,25 degrees.


In the planning of this project it was expected that

  1. measurements on object 1 would mainly demonstrate errors related to positioning and reading the scale of the goniometer,

  2. measurements on object two would include the errors of the first setting, and on top of that also demonstrate the inaccuracy due to the lack of well-defined axis of the thigh and lower leg. The pivot point of the knee joint is also less well-defined and in fact moving during knee flexion. The leg position, though, is ”frozen” in this outline drawing.

  3. further inaccuracy was expected in the ”real life” situation, where the therapists had to decide, when the knee joint was at the fully flexed position. This position with its elastic end-feel is not entirely well- defined, and the test person might also offer resistance or help by co-contraction. Several factors regarding the test person were not considered in this investigation: the effect of repeated measurements, variation during the day, preceding activity, etc. The errors of the first setting were also expected to exist in settings two and three; - errors from two were expected in setting three, but not in setting number one.


Two types of variation were expected:

  • The variation between repeated measurements from the same therapist.  (intra-individual)

  • The variation between the results from different therapists examining the same object (inter-individual)

 The results were described using the median, maximum and minimum.

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See table and graphs 1-3:

1) Object 1 (geometric angle, line drawing)

2) Object 2(outlines of human knee in flexed position)

3) Object 3 (a clinical situation: human knee fully flexed)


 Even though the number of measurements was small, clear tendencies are obvious.

The errors increase from object 1-3, within and between the therapists.

When analysing the variation, the span between maximum and minimum in 1st, 2nd and 3rd object (3, 15, and 35 degrees), it is believed that they have different causes:

  1. 3 degrees stem from placing of the tools and reading of the scale
  2. 15 - 3 degrees = 12 degrees stem from an unclearly defined angle
  3. 35 - 15 = 20 degrees stem from the elasticity of the soft tissues, and the interaction with the test person.

 The individual results of object 3, (span between 7 and 15 degrees), revealed less variation, than occurred between the therapists (35 degrees between the two most extreme measurements.

Let one therapist evaluate, whenever the results need to be compared.

 Errors can be diminished by careful and systematic procedures. A goniometer with longer ”legs”  and a finer scale increased the accuracy.

It would be of great help to secure (fix) the measured angle by drawing the angle to be measured on the skin.

The therapists in this investigation do not use goniometes in their clinical work, but are evaluating range of angular motion by eye, or as a part of a more complex movement:  evaluation of function.

Therefore an extension of this trial was planned: An evaluation of the accuracy of ROM-measurement by eye.

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Pilot-project. K. Grey, 1988. 


This investigation aimed at exploring the variation of articular range of motion (ROM) measured by eye. Six therapists made series of measurements (6-9 each) on two drawn angles.  The intraindividual variation expressed as the span between maximum and minimum was 15 degrees, and  interindividually it was 20 degrees, when evaluating an angle constructed to be 56,5 degrees. The second angle was constructed to be 124,75 degrees and the largest intraindividual variation was 40 degrees.

Measuring ROM requires care to be accurate and reproducable. A goniometer should be preferred to measurement by eye.

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Therapists are using measurement by eye, even though the use of a goniometer is expected to be more accurate. 



Measuring ROM by eye produces inaccurate results with large variation.



Six therapists evaluated twelve drawings (two straight lines forming an angle) three times.

Three of these twelve drawings were identical (V1). Measured by an accurate goniometer they were 56,5 degrees. Two other identical drawings were 124,75 grader (V2).

All the therapists noted readings ending with 0 or 5. The precision was thus only  +/- 2,5 degrees.

In this way each therapist evaluated the drawing ”V1” nine times and “V2”  six times.



The overall average evaluation by eye was 55,3 degrees (”V1”) and 127 degrees (”V2”).

V1:  The largest intraindividual span between min. and max. was 15 degrees and 20 degrees for all.

V2:  The largest intraindividual span was 40 degrees and 40 degrees for all.

When these results are compared to part 1 of this project (goniometer, object 1) where  variations of  2 and 3 degrees were found, when measuring an angle of some 60 degrees it is seen that the intraindividual, the interindividual variation and the round- off- variation makes measurement by eye the least reliable of the two.



Measurement by eye V1, small angle (acute)

Measurement by eyeV2, big angle (obtuse)

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While the average measurements of the two methods are close (+4,77 and -4,01 degrees), the clinical work is affected by large variation from measurement to measurement. A goniometer with ”long legs” and a reading scale of 1 degree divisions is preferred.


External validity:

The measurements by eye in this project were performed on drawings. It would be of more clinical relevance to compare the two methods, when acting on patients.

Moreover, the methods tested here are most useful when used on hinge –joints with a fixed axis. Joints with more complex movement (e.g. vertebral column), with gliding, or rotation, composite movement across several joints (e.g. fingers or shoulder) require other methods.


It seems that the therapists involved in this project often choose to use a more complex approach, where the joint movements are evaluated as part of a more complex movement, situation or goal-oriented specific task.


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