Examination of the Reliability of Joint Angle Measurements Using Image-J:  Errors Involving Rotation

HAYASHI Masanori, HONGOU Yuta

doi:10.1589/rika.25.529

[Purpose] It has been reported that the inter-rater and intra-rater reliability of measuring joint angles with the image processing and analysis software, Image-J, is high; however, it has also been indicated that an error arises when a rotation is involved. Despite this, we could find no reports which examined the scale of the error owing to the degree of rotation. Accordingly, we examined and compared the degree of error in the measured value when set rotations were applied, using a goniometer model and a human model. [Method] With the goniometer as well as the knee flexed at 30°, we took images with a digital camera of the limb position with rotation applied at 10° intervals from 20° internally to 50° abduction. We measured the angles on the obtained images with Image-J and found errors from 30^°. [Results] In the goniometer model, from 20° abduction to 20° internally, and in the human model, from 30° abduction to 20 ° internally, the errors were less than 5°, but outside these ranges errors greater than 5° were found. [Conclusion] At angles greater than 20 ~ 30° abduction, the possibility of measurement errors over 5° with Image-J was high, suggesting that the reliability of the results of 2D analysis with Image-J is low in cases of rotation greater than these.<br>

Examination of the Reliability of Joint Angle Measurements Using Image-J: Errors Involving Rotation

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