Ultrasound Characterization of Patellar Tendon in Non-Elite Sport Players with Painful Patellar Tendinopathy: Absolute Values or Relative Ratios? A Pilot Study

Abstract

Imaging findings in patellar tendinopathy are questioned. The aim of this pilot study was to characterize ultrasound measures, by calculating ultrasound ratio and neovascularization of the patellar tendon in non-elite sport players with unilateral painful patellar tendinopathy. Cross-sectional area (CSA), width, and thickness of the patellar tendon were assessed bilaterally in 20 non-elite sport-players with unilateral painful patellar tendinopathy and 20 asymptomatic controls by a blinded assessor. Ultrasound ratios were calculated to discriminate between symptomatic and asymptomatic knees. The Ohberg score was used for characterizing neovascularization. We found that non-elite sport players with patellar tendinopathy exhibited bilateral increases in CSA, width, and thickness of the patellar tendon compared to asymptomatic controls (Cohen d > 2). The ability of ultrasound ratios to discriminate between painful and non-painful patellar tendons was excellent (receiver operating characteristic, ROC > 0.9). The best diagnostic value (sensitivity: 100% and specificity: 95%) was observed when a width ratio ≥ 1.29 between the symptomatic and asymptomatic patellar tendon was used as a cut-off. Further, neovascularization was also observed in 70% of non-elite sport players with unilateral patellar tendinopathy. A greater CSA ratio was associated with more related-disability and higher tendon neovascularization. This study reported that non-elite sport players with painful unilateral patellar tendinopathy showed structural ultrasound changes in the patellar tendon when compared with asymptomatic controls. Ultrasound ratios were able to discriminate between symptomatic and asymptomatic knees. Current results suggest that ultrasound ratios could be a useful imaging outcome for identifying changes in the patellar tendon in sport players with unilateral patellar tendinopathy.

Keywords: cross-sectional area; patellar tendinopathy; ratios; thickness; ultrasound.

Figure 1

Tendon histogram (tone of grays) confirming the presence of hypoechoic areas in the symptomatic versus the asymptomatic tendon in non-elite sport players. Me: Median value.

Figure 2

Ultrasound assessment of patellar tendon thickness (A), width (B) and cross-sectional area (C).

Figure 3

Intra-tendinous Doppler analysis for identifying neovascularization (A) grade 0: no visible vessels; (B) grade 1: 1 to 2 vessels within the ROI; (C) grade 2: 3 to 5 vessels within the ROI; (D) grade 3: vessels in up to 30% of the ROI. ROI: Region of Interest.

Figure 4

Negative linear association between Cross-Sectional Area (CSA) ratio and related-disability (VISA-P, Victorian Institute of Sport Assessment-Patella score).

Figure 5

Positive linear association between Cross-Sectional Area (CSA) ratio and vascularization grading system.