Walaa S. Mohammad1,2, Faten F. Elattar3, Walaa M. Elsais4, Salameh O. AlDajah4

1Cairo University, Faculty of Physical Therapy, Department of Biomechanics, Giza, Egypt
2Majmaah University, College of Applied Medical Sciences, Department of Physical Therapy, Al-Majmaah, Saudi Arabia
3Cairo University, Faculty of Physical Therapy, Supervisor of Orthopedic Outpatient Clinic, Giza, Egypt
4Isra University, College of Allied Medical Sciences, Department of Physical Therapy, Amman, Jordan

Validity and Reliability of a Smartphone and Digital Inclinometer in Measuring the Lower Extremity Joints Range of Motion

Monten. J. Sports Sci. Med. 2021, 10(2), 47-52 | DOI: 10.26773/mjssm.210907


In clinical settings, available valid and reliable tools are important components in evaluating the lower extremity range of motion. Although the digital inclinometer is highly reliable compared to the universal goniometer, its availability and high cost impede its extensive use. Nowadays, smartphone applications have become widely available to clinicians for assessing the joint range of motion. The present study aims to assess the validity and intra-rater reliability of the smart- phone application “Clinometer” for measuring hip, knee, and ankle sagittal ranges of motion, using the digital inclinom- eter as the reference standard. Active hip, knee flexion and ankle dorsiflexion and plantarflexion range-of-motion mea- surements were recorded in 102 young, healthy female participants on two separate occasions using Clinometer and a digital inclinometer. Pearson’s correlation coefficients (r) were used to evaluate the smartphone application’s validity against the digital inclinometer. To assess the reliability of the Clinometer app, the intra-class correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable difference (MDD) were used. Clinometer displayed excellent validity when compared to the digital inclinometer for hip and knee movements (r>0.90), while ankle ROM displayed moderate validity (r = 0.52-0.57). Additionally, Clinometer demonstrated excellent reliability (ICC > 0.90) for hip and knee sagittal plane motion and moderate reliability for the ankle sagittal plane motion (ICC = 0.53–0.67). Cli- nometer is a portable, low-cost, valid, and reliable tool for assessing active hip and knee range of motions and can be easily incorporated into clinical settings; however, it cannot be used interchangeably for ankle measures.


smartphone application; digital inclinometer; ROM; validity and reliability; lower limb joints

View full article
(PDF – 187KB)


Alawna, M. A., Unver, B. H., & Yuksel, E. O. (2019). The Reliability of a Smartphone Goniometer Application Compared With a Traditional Goniometer for Measuring Ankle Joint Range of Motion. Journal of the American Podiatric Medical Association, 109(1), 22-29. https://doi.org/10.7547/16-128

Behnoush, B., Tavakoli, N., Bazmi, E., Nateghi Fard, F., Pourgharib Shahi, M. H., Okazi, A., & Mokhtari, T. (2016). Smartphone and Universal Goniometer for Measurement of Elbow Joint Motions: A Comparative Study. Asian Journal of Sports Medicine, 7(2), e30668. https://doi.org/10.5812/asjsm.30668

Bhattacherjee, A. (2012). Social science research: Principles, methods, and practices.

Bland, J. M., & Altman, D. G. (1996). Statistics Notes: Measurement error and correlation coefficients. BMJ, 313(7048), 41-42. https://doi.org/10.1136/bmj.313.7048.41

Boone, D. C., Azen, S. P., Lin, C.-M., Spence, C., Baron, C., & Lee, L. (1978). Reliability of goniometric measurements. Physical Therapy, 58(11), 1355-1360. https://doi.org/10.1093/ptj/58.11.1355

Brosseau, L., Tousignant, M., Budd, J., Chartier, N., Duciaume, L., Plamondon, S., . . . Balmer, S. (1997). Intratester and intertester reliability and criterion validity of the parallelogram and universal goniometers for active knee flexion in healthy subjects. Physiotherapy Research International, 2(3), 150-166. https://doi.org/10.1002/pri.97

Campbell, M. J., & Swinscow, T. D. V. (2011). Statistics at square one: John Wiley & Sons.

Carey, M. A., Laird, D. E., Murray, K. A., & Stevenson, J. R. (2010). Reliability, validity, and clinical usability of a digital goniometer. Work, 36(1), 55-66. https://doi.org/10.3233/WOR-2010-1007

Charlton, P. C., Mentiplay, B. F., Pua, Y. H., & Clark, R. A. (2015). Reliability and concurrent validity of a Smartphone, bubble inclinometer and motion analysis system for measurement of hip joint range of motion. Journal of Science and Medicine in Sport, 18(3), 262-267. https://doi.org/10.1016/j.jsams.2014.04.008

Derhon, V., Santos, R. A., Brandalize, M., Brandalize, D., & Rossi, L. P. (2017). Intra- and inter-examiner reliability in angular measurements of the knee with a smartphone application. Human Movement, 18(2), 38-43. https://doi.org/10.1515/humo-2017-0011

Gajdosik, R. L., & Bohannon, R. W. (1987). Clinical measurement of range of motion: review of goniometry emphasizing reliability and validity. Physical Therapy, 67(12), 1867-1872. https://doi.org/10.1093/ptj/67.12.1867

Gogia, P. P., Braatz, J. H., Rose, S. J., & Norton, B. J. (1987). Reliability and validity of goniometric measurements at the knee. Physical Therapy, 67(2), 192-195. https://doi.org/10.1093/ptj/67.2.192

Gouveia, V. H. d. O., Araújo, A. G. d. F., Maciel, S. d. S., Ferreira, J. J. d. A., & Santos, H. H. d. (2014). Reliability of the measures inter and intra-evaluators with universal goniometer and fleximeter. Fisioterapia e Pesquisa, 21, 229-235. https://doi.org/10.590/1809-2950/52921032014

Hambly, K., Sibley, R., & Ockendon, M. (2012). Level of agreement between a novel smartphone application and a long arm goniometer for the assessment of maximum active knee flexion by an inexperienced tester. International Journal of Physiotherapy & Rehabilitation, 2.

Jones, A., Sealey, R., Crowe, M., & Gordon, S. (2014). Concurrent validity and reliability of the Simple Goniometer iPhone app compared with the Universal Goniometer. Physiotherapy Theory and Practice, 30(7), 512-516. https://doi.org/10.3109/09593985.2014.900835

Mehta, S. P., Barker, K., Bowman, B., Galloway, H., Oliashirazi, N., & Oliashirazi, A. (2017). Reliability, Concurrent Validity, and Minimal Detectable Change for iPhone Goniometer App in Assessing Knee Range of Motion. Journal of Knee Surgery, 30(6), 577-584. https://doi.org/10.1055/s-0036-1593877

Milanese, S., Gordon, S., Buettner, P., Flavell, C., Ruston, S., Coe, D., . . . McCormack, S. (2014). Reliability and concurrent validity of knee angle measurement: smart phone app versus universal goniometer used by experienced and novice clinicians. Manual Therapy, 19(6), 569-574. https://doi.org/10.1016/j.math.2014.05.009

Mitchell, K., Gutierrez, S. B., Sutton, S., Morton, S., & Morgenthaler, A. (2014). Reliability and validity of goniometric iPhone applications for the assessment of active shoulder external rotation. Physiotherapy Theory and Practice, 30(7), 521-525. https://doi.org/10.3109/09593985.2014.900593

Norkin, C. C., & White, D. J. (2016). Measurement of joint motion: a guide to goniometry: FA Davis.

Ockendon, M., & Gilbert, R. E. (2012). Validation of a novel smartphone accelerometer-based knee goniometer. Journal of Knee Surgery, 25(4), 341-345. https://doi.org/10.1055/s-0031-1299669

Pereira, L. C., Rwakabayiza, S., Lécureux, E., & Jolles, B. M. (2017). Reliability of the Knee Smartphone-Application Goniometer in the Acute Orthopedic Setting. Journal of Knee Surgery, 30(3), 223-230. https://doi.org/10.1055/s-0036-1584184

Portney, L. G., & Watkins, M. P. (2009). Foundations of clinical research: applications to practice (Vol. 892): Pearson/Prentice Hall Upper Saddle River, NJ.

Rabin, A., Kozol, Z., & Finestone, A. S. (2014). Limited ankle dorsiflexion increases the risk for mid-portion Achilles tendinopathy in infantry recruits: a prospective cohort study. J Foot Ankle Res, 7(1), 48. https://doi.org/10.1186/s13047-014-0048-3

Roach, S., San Juan, J. G., Suprak, D. N., & Lyda, M. (2013). Concurrent validity of digital inclinometer and universal goniometer in assessing passive hip mobility in healthy subjects. International Journal of Sports Physical Therapy, 8(5), 680.

Rome, K., & Cowieson, F. (1996). A reliability study of the universal goniometer, fluid goniometer, and electrogoniometer for the measurement of ankle dorsiflexion. Foot and Ankle International, 17(1), 28-32. https://doi.org/10.1177/107110079601700106

Rothstein, J. M., Miller, P. J., & Roettger, R. F. (1983). Goniometric reliability in a clinical setting: elbow and knee measurements. Physical Therapy, 63(10), 1611-1615. https://doi.org/10.1093/ptj/63.10.1611

Santos, C. M. d., Ferreira, G., Malacco, P. L., Sabino, G. S., Moraes, G. F. d. S., & Felício, D. C. (2012). Confiabilidade intra e interexaminadores e erro da medição no uso do goniômetro e inclinômetro digital. Revista Brasileira de Medicina do Esporte, 18, 38-41. https://doi.org/10.1590/S1517-86922012000100008

Swisher, L. L., & Hiller, P. (2010). The revised APTA code of ethics for the physical therapist and standards of ethical conduct for the physical therapist assistant: theory, purpose, process, and significance. Physical Therapy, 90(5), 803-824. https://doi.org/10.2522/ptj.20090373

Vohralik, S. L., Bowen, A. R., Burns, J., Hiller, C. E., & Nightingale, E. J. (2015). Reliability and validity of a smartphone app to measure joint range. American Journal of Physical Medicine and Rehabilitation, 94(4), 325-330. https://doi.org/10.1097/phm.0000000000000221

Watkins, M. A., Riddle, D. L., Lamb, R. L., & Personius, W. J. (1991). Reliability of goniometric measurements and visual estimates of knee range of motion obtained in a clinical setting. Physical Therapy, 71(2), 90-96. https://doi.org/10.1093/ptj/71.2.90

Weir, J. P. (2005). Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. Journal of Strength and Conditioning Research, 19(1), 231-240. https://doi.org/10.1519/15184.1

Wellmon, R. H., Gulick, D. T., Paterson, M. L., & Gulick, C. N. (2016). Validity and Reliability of 2 Goniometric Mobile Apps: Device, Application, and Examiner Factors. J Sport Rehabil, 25(4), 371-379. https://doi.org/10.1123/jsr.2015-0041

Williams, C. M., Caserta, A. J., & Haines, T. P. (2013). The TiltMeter app is a novel and accurate measurement tool for the weight bearing lunge test. Journal of Science and Medicine in Sport, 16(5), 392-395. https://doi.org/10.1016/j.jsams.2013.02.001

Wojciechowski, M. (2011). How technology is being used in PT and PTA education. PT in Motion, 3(9), 18-24.