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Yes you can measure your knee range of motion at home and yes it is as accurate as a physical therapist measuring your knee range of motion.

This is the exact questions we started with when we compared knee range of motion measured using the Curovate app to a licensed physical therapist measuring using a goniometer. A goniometer is a tool that physical therapists use to measure how far a part of your body bends or straightens.[1] We have published our technical report in the International Journal of Sport Physical Therapy in the April 2022 publication HERE.[2]

In this blog post I will discuss exactly how we compared Curovate's in-app knee range of motion measurement with the measurements taken by a licensed physical therapist and the results of this research.[2]

How did we compare the app measurement and physical therapist's measurements?

We started with 4 positions of flexion, this is where the knee is bent, and 4 positions of extension, this is where the knee is straight or almost straight. If you want to learn more about knee range of motion check out our previous blog here. We measured each position with an iPhone 11, iPhone XR, iPad Pro, Android Samsung S7 and a licensed physical therapist with 20 years of clinical experience. We measured a total of 8 positions of flexion and extension and then we repeated the measurements again for a total of 80 measurements.[2] We were looking for both the reliability, how consistent was each measurement with each device or method for the same knee position, and the correlation, how closely did the different methods of measurement match.[2] The reason we used 3 mobile devices and 1 tablet all running on different operating systems was because we wanted to know if the size and shape of the device, the different sensors that are in each device and the software that operates each device would change the knee range of motion measurements using Curovate. Previous researchers have shown that in-app measurements are NOT reliable across different mobile devices running the same app.[3]

What did we find when we compared the knee range of motion measurements?

We found that there was consistency among all 4 devices as well as the physical therapist's measurements. How consistent? There is a simple statistical measure called Pearson's Correlation which measures the correlation between two things.[4] The Pearson's Correlation can be between -1 to +1. If a correlation is -1 then it means that as one number goes up the other goes down. If the correlation is 0 then it means that there is no correlation and if the value is +1 then it means there is a very strong positive correlation.[4] In our study we found that all of the correlations were either 0.998 or higher.[2] This means that the values produced by all 4 mobile devices as well as the physical therapist were highly correlated.[2] I have provided the correlation table from the study below.

Table #1 - the correlation matrix for standard goniometric measurement (measured by a licensed physical therapist) compared to the 4 mobile devices measuring knee flexion and extension at 8 different positions each measured twice. This table shows a positive correlation among mobile devices as well as with standard goniometric measurements. Note that where the table would compare the same device to itself you will see the number 1 and the grey sections are omitted to avoid repetition on this table.2

Why does this research matter to me? What does this mean for my knee measurements using Curovate?

This study was a technical report and therefore it means that this is the first step in validating the in-app knee range of motion measurement you can obtain using the Curovate app.[2] This study demonstrates that with one person or research subject and one physical therapist there is a strong correlation and reliability of the in-app knee range of motion measurement using Curovate.[2] Also this study shows that across 4 different devices, iOS and Android, all with different operating systems and of various size and shape the knee range of motion measurement was consistent for flexion and extension.[2] So you do not need to worry if you have an iPhone an iPad or an Android device and you are using it to measure your knee range of motion because they should all produce very similar knee range of motion measurements.

Our next steps are to reproduce this study with people who have actually had knee injury and surgery and to assess the measurement when people complete this measurement on their own knee. Our next blog will demonstrate how you can use our research technique to obtain accurate knee range of motion measurements. There are some tips and tricks we used in this study that you can do at home to get the most accurate self measurement of your knee range of motion. Comment below and let us know what you think of this study and how confident you are taking your own knee range of motion measurements. If you want to watch a simple video demonstration of how to use Curovate to measure your knee range of motion click HERE.

Conclusion

You can measure your knee range of motion using the Curovate app. You can download the Curovate app from the links below. Curovate provides you with a simple way to measure knee range of motion without the need for any additional devices or wearables. Simply use the Curovate app on your smartphone and you can obtain your knee range of motion in less than 30 seconds. The technical report published in the International Journal of Sport Physical Therapy in April 2022 demonstrates that there is a very strong positive correlation when using Curovate on 4 different mobile devices and comparing the measurements to a physical therpaist measuring knee range of motion.[2] The correlation in this techniical report was 0.998 or higher in all 80 measurements.[2] A correlation of +1 means that the two measures are strongly correlated and a correlation of 0 means there is no correlation between the measurements.

Do you want a simple way to measure your knee range of motion at home? Try the Curovate app, an evidence-based app that will provide you with a physical therapy plan, guided video exercises, and the ability to measure your knee range of motion! Download Curovate today by clicking the links below!

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References

1. Physiopedia. Goniometer. Accessed Augsut 25, 2022.

2. Shah N, Grunberg C, Hussain Z. Can a Patient use an App at Home to Measure Knee Range of Motion? Utilizing a Mobile App, Curovate, to Improve Access and Adherence to Knee Range of Motion Measurements. IJSPT. 2022;17(3):541-547. doi:10.26603/001c.33043

3. Keogh JWL, Cox A, Anderson S, et al. Reliability and validity of clinically accessible smartphone applications to measure joint range of motion: a systematic review. PLoS ONE. 2019;14(5):e0215806. doi:10.1371/journal.pone.0215806

4. Nettleton D. Commercial Data Mining. Selection of Variables and Factor Derivation. Science Direct. Elsevier; 2014. doi: https://doi.org/10.1016/C2013-0-00263-0