Determination of differences in ultrasound parameters for patellar tendons in males with unilateral patellar tendinopathy—An ancillary analysis of data from two randomized controlled trials

Purpose: To investigate power Doppler (PD) activity and tendon structure (betweenthe injured and contralateral limb) in patients with unilateral patellar tendinopathy(PT) using ultrasonography (US). Secondly, the aim was to determine the intra-raterreliability of the PD activity and tendon structure. Methods: This study analyzed US baseline data from 57 male participants with symp-tomatic unilateral PT who had been enrolled in one of two randomized clinical trials.Data were analyzed to examine if systematic differences existed between injuredand contralateral limbs using Fiji ImageJ. Results: The PD activity of the symptomatic tendon was larger 25.6 (Q1=14.9;Q3=41.6) mm2than the asymptomatic 0 (Q1=0.0; Q3=0.0) mm2(p< 0.001).There was a significantly greater tendon thickness at the proximal (2.5 mm 95% CI[2.0; 3.0]), mid (0.8 mm 95% CI [0.5; 1.1]), and distal (0.2 mm 95% CI [0.1; 0.4]) partof the tendon for the symptomatic compared to the asymptomatic tendon. Intra-raterreliability for PD activity and tendon structure ranged from moderate-to-excellent(0.74; 0.99). Conclusion: These results provide mean estimates for tendon thickness of symptom-atic and asymptomatic tendons, that can be used for clinicians to reliably estimatepathological tendon thickness.