Abstract
Objectives(1) To determine the association between patellar tendon stiffness and the presence of patellar tendinopathy (PT). (2) To evaluate the reliability of shear-wave elastography (SWE).MethodsParticipants were consecutively enrolled between January 2017 and June 2019. PT was diagnosed clinically and confirmed by either grayscale US or power Doppler US, or both. Controls had no history of anterior knee pain and no clinical signs of PT. Patellar tendon stiffness (kilopascal, kPa) was assessed using SWE. Logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Reliability analyses included coefficients-of-variation (CV), coefficients-of-repeatability (CR), intraclass correlation coefficient (ICC) for intraobserver and interobserver reliability, and Bland-Altman analysis.ResultsIn total, 76 participants with PT (58 men, mean age 24.4 ± 3.8 years) and 35 asymptomatic controls (16 men, mean age 21.5 ± 3.8 years) were included. Univariate analyses (OR 1.094, 95% CI 1.061–1.128, p < .001) and adjusted multivariate analyses (OR 1.294, 95% CI 1.044–1.605, p = .018) showed that athletes with PT had significantly increased patellar tendon stiffness. ICC for intraobserver reliability was 0.95 (95% CI 0.92–0.97), CR (CV) 12 kPa (10%) and 0.79 (95% CI 0.65–0.88), CR (CV) 18 kPa (21%) for interobserver reliability. Mean differences from Bland-Altman analysis were 5.6 kPa (95% CI 3.1–8.1, p < .001) for intraobserver reliability and 4.6 kPa (95% CI 1.9–7.2, p < .001) for interobserver reliability.ConclusionsPT is associated with significantly higher patellar tendon stiffness. SWE measurements demonstrate excellent intraobserver reliability and good interobserver reliability. Therefore, SWE is a promising tool to implement in longitudinal studies and future studies should evaluate its prognostic value and utility as a monitoring tool in athletes with PT.Key Points• Patellar tendon stiffness measured with shear-wave elastography (SWE) is higher in athletes with patellar tendinopathy than in healthy controls, also after adjusting for potential confounders.• Excellent intraobserver reliability and good interobserver reliability were found for the quantitative assessment of patellar tendon stiffness using SWE.
Highlights
Patellar tendinopathy (PT) is an overuse injury of the patellar tendon resulting in pain, decreased exercise tolerance, and impaired function [1]
The intraobserver reliability analysis (Table 4) revealed an intraclass correlation coefficient (ICC) of 0.95 for the median patellar tendon stiffness using all ROIs between analysis 1 and analysis 2
In this study on the implementation of shear-wave elastography (SWE) on the patellar tendon in jumping athletes with patellar tendinopathy and activity-matched controls, we found that patellar tendinopathy was associated with significantly higher patellar tendon stiffness, both in univariate analyses and in adjusted multivariate analyses
Summary
Patellar tendinopathy (PT) is an overuse injury of the patellar tendon resulting in pain, decreased exercise tolerance, and impaired function [1]. There is consensus that PT is a clinical diagnosis with focal load-related pain, established by medical history taking and clinical examination. The applicability of ultrasound (US) is limited to confirming the clinical diagnosis of PT by assessing morphological changes [3]. Tendinopathy-related abnormalities on US are tendon thickening with hypoechoic areas and/or increased Doppler flow [4, 5]. These alterations are associated with tendinopathy; they have been reported in up to 59% of asymptomatic athletes [6]. Changes in tendon structure on grayscale US (GSUS) are considered a risk factor for tendinopathy rather than indicative for PT or tendon pain [7]. Alternative imaging techniques that better reflect pain remain to be investigated as they could provide attractive novel biomarkers to assess therapy response
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