Fig. 2.

Grayscale US and corresponding shear-wave elastograms in an asymptomatic athlete and an athlete with patellar tendinopathy. a, d Longitudinal grayscale ultrasound images of the proximal patellar tendon in an asymptomatic 19-year-old male basketball player (a) and in a 21-year-old male basketball player with patellar tendinopathy (d). a shows normal alignment of collagen bundles, whereas d shows disruption of the normal tendon architecture with hypoechoic areas separating collagen bundles. b, e Elastograms depicted as an overlay on grayscale images where user settings defined red as stiff tissues and blue as soft tissues. Pronounced red areas (indicating increased stiffness) were typically observed in the proximal patellar tendon of participants with patellar tendinopathy (e), compared to predominantly light blue areas (representing intermediate elasticity) in asymptomatic athletes (b). Dark blue areas posterior to the patellar tendon correspond to the relative soft Hoffa’s fatpad. The small red area at the left border in both b and e corresponds to the inferior patellar border and was excluded for quantitative analysis. c, f Multiple partially overlapping circular regions of interest were placed for quantitative analysis of tendon stiffness, covering the proximal 20 mm of the patellar tendon (referred by reference ruler), starting 5 mm distal to the inferior patellar pole. The median stiffness (interquartile range) of the proximal patellar tendon in the asymptomatic athlete (c) was 30.6 kPa (29.3–32.2) and in the athlete with patellar tendinopathy (f) 117.4 kPa (112.3–133.8)