Smartphone goniometer has excellent reliability between novice and experienced physical therapists in assessing knee range of motion.

INTRODUCTION: Smartphone app-based goniometer (SG) are emerging as an alternative to Universal Goniometers (UG) in assessing joint range of motion (ROM). This study examined whether the experience level of examiner affected the reliability of assessing knee flexion (KF) and knee extension (KE) ROM using UG and SG.

METHODS: Participants with osteoarthritis of the knee or following total knee replacement were recruited. KF and KE ROM using UG and SG were assessed twice by an experienced physical therapist (PT) and a student PT (SPT). Intraclass correlation coefficients (ICC) examined the interrater (experienced PT vs SPT) and intrarater reliabilities (for experienced PT and SPT) in assessing KF and KE ROM for UG and SG. Concurrent relationships were examined between the knee ROM with pain and physical function using Pearson Correlation Coefficient (r).

RESULTS: The interrater reliability in assessing KF and KE ROM was excellent (ICC>0.90) between novice and experienced examiners. The standard error of measurement (SEM) for novice examiner in assessing KF was 1° and 2° while using UG and SG respectively; whereas the SEM for experienced examiner in assessing KF was 1° irrespective of which device was used. The concurrent relationships between KF and KE ROM with measures of pain and function were divergent (moderate to low correlations; r <0.7; p > 0.05).

CONCLUSION: Both UG and SG have smaller measurement error in assessing KF and KE ROM irrespective of experience level of examiner and therefore no one tool is superior than the other for assessing knee ROM in clinical practice.