Ultrasound Assessment of Weight-Bearing and Non–Weight-Bearing Meniscal Extrusion: A Reliability Study

Background: Ultrasound has become a useful instrument in evaluating musculoskeletal pathology. Recent studies suggest that ultrasound imaging of weight-bearing menisci may enhance the assessment of knee pathology, such as osteoarthritis (OA) and meniscal injuries. Objective: The primary aim of this study was to determine the intrarater and interrater reliability of ultrasound measurements of medial meniscal extrusion (MME) after a brief training session. Design: Prospective reliability study. Setting: Physical medicine and rehabilitation (PM&R) department within a tertiary care institution. Participants: Forty-five participants (29 female, 16 male) were recruited to serve as models, 24 of whom had healthy knees and 21 of whom had radiographically confirmed medial compartment knee OA. Three physician sonographers (1 = experienced, 1 = sports medicine fellow, 1 = post-graduate year [PGY]-4 PM&R resident) were recruited to serve as operators. Methods or Interventions: Operators received a brief training session on identifying and measuring MME. All operators measured bilateral MME in each model in the standing and supine positions on two separate days. Operators were blinded to all measurements. Main Outcome Measurements: Primary outcomes were inter- and intrarater intraclass correlation coefficients (ICCs) of MME measurements among operators with different levels of ultrasound experience. Results: Supine MME intrarater reliability ICCs were 0.927, 0.885, and 0.780 for the experienced physician, sports medicine fellow, and PGY-4 operators, respectively. Standing MME intrarater reliability ICCs were 0.941, 0.902, and 0.824 for the experienced physician, sports medicine fellow, and PGY-4 operators, respectively. Interrater reliability ICCs were 0.896 and 0.842 for supine and standing measurements, respectively. There was a statistically significant increase in intrarater reliability with experience between the PGY-4 resident and experienced physician operators. Conclusions: Operators with different levels of ultrasound experience demonstrated good MME measurement intra- and interrater reliabilities in both supine and standing positions.