Patellar mobility can be reproducibly measured using ultrasound

The present study was performed to examine the reliability of ultrasound in evaluating patellar mobility in the superior–inferior direction. Twelve healthy men volunteered for the study. Patellar mobility in the superior–inferior direction during isometric knee extension contraction with the knee immobilized in a semi-flexed knee brace was measured using ultrasound. Both intra-observer and inter-observer reliability were assessed by intra-class correlation coefficients (ICCs). Bland–Altman analysis was used for assessing agreement between measurements. ICC values were excellent for both intra-observer and inter-observer reliability at 0.97 and 0.93, respectively. In 95 % of measurements, the same observer measured within −0.55 to 0.61 mm, while different observers measured within −0.82 to 0.85 mm. In conclusion, patellar mobility in the superior–inferior direction during an isometric knee extension exercise can be reproducibly measured using ultrasound. The level of evidence VI (basic study of a novel evaluation method).