Reliability of measuring the medial knee joint space using ultrasound imaging

Background: The use of ultrasound to perform quantitative musculoskeletal (MSK) measurements requires reliability among different providers with varied levels of experience and training. Recent studies have shown that physical therapists (PT) can reliably measure the glenohumeral joint space using ultrasound imaging (USI) and operator experience or well defined training protocols influences the reliability. Few studies have reported the reliability of medial knee gap measurements with USI. Objective: Evaluate inter- and intra-rater reliability of a novel approach to measuring knee gapping using experienced and trained novice clinicians. Design: Inter-rater and intra-rater reliability study Setting: Physical therapy program Participants: Novice researchers were three upper-year Doctor of Physical Therapy students. Experienced researchers were two PT certified in MSK USI with eight years of experience. Methods: A total of 166 images of two subject’s medial knee joint gaps were captured in resting by a single experience researcher. Three novice researchers, who underwent a three-hour training protocol and two experienced researchers measured the images individually. Measurements were taken using standardized bony landmarks and internal calipers. All researchers were blinded to the subjects and results. Main outcome measures: Data was analyzed using two-way ICC mixed-model single measurement, SEM run for all researchers compared with experienced researcher one. Results: An excellent degree of reliability was found for both intra-rater and inter-rater measurements for Novice One and a good degree of reliability was found between Experienced One and Novice Two and Three. Conclusion: Both experienced and novice researchers attained a clinically significant ICC when compared to Experienced One. An accurate and reliable measurement of the medial knee joint gap maybe useful for further studies and help with diagnosis of joint pathologies. Level of study: IIB