title: Reliability, Concurrent Validity, and Minimal Detectable Change for iPhone Goniometer App in Assessing Knee Range of Motion.
abstract: Much of the published works assessing the reliability of smartphone goniometer apps (SG) have poor generalizability since the reliability was assessed in healthy subjects. No research has established the values for standard error of measurement (SEM) or minimal detectable change (MDC) which have greater clinical utility to contextualize the range of motion (ROM) assessed using the SG. This research examined the test-retest reproducibility, concurrent validity, SEM, and MDC values for the iPhone goniometer app (i-Goni; June Software Inc., v.1.1, San Francisco, CA) in assessing knee ROM in patients with knee osteoarthritis or those after total knee replacement. A total of 60 participants underwent data collection which included the assessment of active knee ROM using the i-Goni and the universal goniometer (UG; EZ Read Jamar Goniometer, Patterson Medical, Warrenville, IL), knee muscle strength, and assessment of pain and lower extremity disability using quadruple numeric pain rating scale (Q-NPRS) and lower extremity functional scale (LEFS), respectively. Intraclass correlation coefficients (ICCs) were calculated to assess the reproducibility of the knee ROM assessed using the i-Goni and UG. Bland and Altman technique examined the agreement between these knee ROM. The SEM and MDC values were calculated for i-Goni assessed knee ROM to characterize the error in a single score and the index of true change, respectively. Pearson correlation coefficient examined concurrent relationships between the i-Goni and other measures. The ICC values for the knee flexion/extension ROM were superior for i-Goni (0.97/0.94) compared with the UG (0.95/0.87). The SEM values were smaller for i-Goni assessed knee flexion/extension (2.72/1.18 degrees) compared with UG assessed knee flexion/extension (3.41/1.62 degrees). Similarly, the MDC values were smaller for both these ROM for the i-Goni (6.3 and 2.72 degrees) suggesting smaller change required to infer true change in knee ROM. The i-Goni assessed knee ROM showed expected concurrent relationships with UG, knee muscle strength, Q-NPRS, and the LEFS. In conclusion, the i-Goni demonstrated superior reproducibility with smaller measurement error compared with UG in assessing knee ROM in the recruited cohort. Future research can expand the inquiry for assessing the reliability of the i-Goni to other joints.
authors.affiliation: School of Physical Therapy, Marshall University, Huntington, West Virginia.|Department of Orthopedic Surgery, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia.
authors.forename: Saurabh P
authors.initials: SP
authors.lastname: Mehta
authors.affiliation: School of Physical Therapy, Marshall University, Huntington, West Virginia.
authors.forename: Katherine
authors.initials: K
authors.lastname: Barker
authors.affiliation: SOMC LIFE Center, Southern Ohio Medical Center, Portsmouth, Ohio.
authors.forename: Brett
authors.initials: B
authors.lastname: Bowman
authors.affiliation: Department of Physical Therapy, Elk Valley Physical Therapy, Elkview, West Virginia.
authors.forename: Heather
authors.initials: H
authors.lastname: Galloway
authors.affiliation: Department of Orthopedic Surgery, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia.
authors.forename: Nicole
authors.initials: N
authors.lastname: Oliashirazi
authors.affiliation: Department of Orthopedic Surgery, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia.
authors.forename: Ali
authors.initials: A
authors.lastname: Oliashirazi
mesh_terms: D000368:Aged; D053587:Arthrometry, Articular / Q000295:instrumentation*; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D035002:Lower Extremity; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D000068997:Smartphone