Objective: The aim of this study is to examine the validity and reliability of a wearable motion sensor, which is an inertial measurement units (IMUs) sensor, in measuring knee joint active flexion movement angles.

Methods: The study included 70 Health Sciences Faculty students between the ages of 18-25. The dominant knee joint range of motion of the participants was measured by two raters with a digital goniometer (Meloq EasyAngle) and wearable motion sensors (MetaMotionRL). A 10-minute rest was given between each measurement. The data were analyzed using the IBM® SPSS® Statistics for Windows software (Version 27.0). Mean ± standard deviation (Mean ± SD) and percentage (%) were used for the descriptive variables. Intra- and inter-rater reliability was tested with intraclass correlation coefficient (ICC) and Bland-Altman analysis. ICC values less than 0.5 were classified as poor, values between 0.5 and 0.75 as moderate, values between 0.75 and 0.9 as good, and values greater than 0.90 as excellent reliability. Paired samples t test was used to compare test-retest measurements. Concurrent validity was determined by Pearson correlation coefficient. The significance value was accepted as p<0.05.

Before knee range of motion measurements, all participants were given verbal information about the measurements. Participants were asked to wear shorts that exposed their knees. While the participants were lying in the prone position on the examination table, their dominant knee range of motion was measured with both EasyAngle and MetaMotionRL by two different physiotherapists.

EasyAngle digital goniometer and universal goniometer measurement results were compared and it was concluded that EasyAngle is a valid and reliable evaluation tool.

MetaMotionRL (MBientlab Inc., San Francisco, USA); Includes 9-axis inertial measurement units and environmental monitoring sensor. It features gyroscope, accelerometer, magnetometer and sensor fusion. Real-time communication is provided via BluetoothLE. Data can also be saved to 8 megabyte NOR flash memory. There are free, open-source applications and applications for fast data collection.

Inclusion Criteria:

• being between the ages of 18-25
• volunteering to participate in the study

Exclusion Criteria:

• a history of orthopedic surgery or trauma to the lower extremity
• knee pain felt during joint range of motion measurement
• inability to maintain a prone position

Seventy healthy student were included between December 2021 and April 2022, the study was approved by Haliç University Non-Invasive Ethics Committee (173/01.12.2021). All participants completed written informed consent. Seventy healthy students (40 female, 30 male) from Haliç University Faculty of Health Sciences were included in the study.