Validation of a Novel Smartphone Accelerometer-Based Knee Goniometer
Ockendon M & Gilbert RE. J Knee Surg. 2012 Sep;25(4):341-5.
Measuring knee range of motion (ROM) is a common clinical practice among most healthcare professionals, especially when monitoring ROM to track post-surgical outcomes. Goniometers, accelerometers, and inclinometers are some examples of instruments that have been used to assess knee ROM. Smartphones have built in accelerometers for various uses; therefore, the purpose of this study was to evaluate the reliability of a Smartphone knee goniometry application for assessing knee ROM. The authors designed an application for the iPhone (“Knee Goniometer”) that estimates knee ROM by utilizing tibial incline measurements and basic trigonometry when placing the phone on the mid-shaft of the tibia. Two independent and blinded clinicians measured 3 simulated joint angles bilaterally in 5 healthy males utilizing the iPhone application as well as a goniometer. The intra- and inter-observer reliability of a traditional goniometer were excellent with correlations of 0.93 and 0.95 and standard errors of ± 9.6 degrees and ± 8.4 degrees, respectively. In comparison, the intra-and inter-observer reliability of the iPhone application were mildly better with correlations of 0.98 and 0.99 and standard errors of ± 4.6 degrees and ± 2.7 degrees, respectively. The authors found there was a high correlation between instruments (r = 0.95) and a mean difference of only -0.04 degrees.
Clinically, the athletic trainer may have a valid and reliable application readily available in their pockets for clinical ROM knee measurements. Truthfully, the smartphone may take out some of the ambiguity and user error often associated with the use of a traditional goniometer, potentially providing a more accurate and universally accepted method to measure ROM. The possible implications of an application like this could mean more accurate interobserver results. Furthermore, this method for measuring ROM could have implications on the compliance and monitoring of ROM during home exercise programs. Athletes may be able to track and report their ROM to the clinician daily, or even multiple times throughout the day. However, there results should be interpreted with mild caution. Interestingly, the authors of the paper are the creators of the application “Knee Goniometer.” Curiosity led me to the App Store for independent investigation of this potentially useful application. Much to my surprise, the application could be purchased for $4.99. While the authors did demonstrate that this application was valid and reliable in comparison to currently utilized clinical knee ROM measures, they have a bias in conducting this research as it has a financial implication to them personally. It would have been more interesting to see a third party, independent group investigate the clinical usefulness of this application. Does anyone have any experience with an application like this? Furthermore, does anyone have any smartphone applications that they find clinically useful?
Written by: Nicole Cattano
Reviewed by: Stephen Thomas