DrG was proven to be a valid and reliable tool in measuring knee ROM following arthroplasty. DrG showed good intrarater reliability and excellent inter-rater reliability for flexion (intraclass correlation coefficient=0.990 and 0.990) and good reliability for extension (intraclass correlation coefficient=0.897 and 0.899). The goniometer and DrG showed strong correlations for flexion (r=0.94) and extension (r=0.90). A total of 60 images of knee ROM for 30 unicondylar or total knee arthroplasty were assessed. To examine reliability, four clinicians assessed each image using DrG on four separate occasions spaced 1 week apart. To assess validity, the patient’s knee was measured by a clinician using a goniometer. Participants then rated the ease of participation. A smartphone camera was used to take photographs of the knee in full flexion and full extension, and the images were sent by participants to a study phone. The aim was to determine the concurrent reliability and validity of the photo-based application ‘Dr Goniometer’ (DrG) compared with a universal goniometer performed by a clinician. Smartphone technology has led to the creation of applications that can measure ROM. Knee range of motion (ROM) following a knee arthroplasty is an important clinical outcome that directly relates to the patient’s physical function.
