BACKGROUND: This study aimed to assess the mid-term effects of focused extracorporeal shockwave therapy (ESWT) on clinical symptoms and tendon structure in patellar tendinopathy. Ultrasound (US) evaluation and an innovative in vivo analysis of intra-tendinous morphology using validated spatial frequency analysis (SFA) software were employed to quantify the organization and density of collagen fascicles. METHODS: This prospective cohort study included 21 recreational athletes (mean age 29.9 ± 9.3 years) with chronic unilateral symptomatic patellar tendinopathy. ESWT was applied as monotherapy over four weekly sessions. Pain was assessed using the Numeric Rating Scale (NRS) and disease severity with the Victorian Institute of Sports Assessment - Patella (VISA-P) questionnaire. Morphological parameters, such as tendon diameter (TD), were assessed with US and analyzed using SFA software. The asymptomatic tendons served as controls. Follow-up assessments were conducted at the end of the treatment period and 3 months posttreatment. RESULTS: Baseline evaluations revealed increased TD in proximal part of the tendon ( P = 0.001) and decreased organization of collagen fascicles ( P = 0.013) in symptomatic tendons compared to asymptomatic controls. At the 3-month follow-up, symptomatic tendons showed significant reductions in TD ( P < 0.001) and improvements in both organization and density of collagen fascicles throughout various parameters - peak spatial frequency radius (PSFR) ( P = 0.024), P6 ( P = 0.05), Q6 ( P = 0.016), PPP ( P = 0.003). No significant morphological changes were observed in asymptomatic tendons. Clinical evaluations demonstrated significant reductions in NRS ( P < 0.001) and increases in Victorian Institute of Sports Assessment - Patella (VISA-P) scores ( P < 0.001) at all time points. CONCLUSION: The study suggests that ESWT may have the potential to induce positive structural changes in patellar tendinopathy, including improved organization and density of collagen fascicles. These findings indicate that ESWT could be a promising noninvasive approach to managing patellar tendinopathy, with observed improvements in clinical symptoms and tendon structure. However, further high-quality research is needed to confirm these results and establish their long-term efficacy.

2nd Faculty of Medicine Department of Rehabilitation and Sports Medicine Charles University and University Hospital Motol Prague Czech Republic

Department of Biological Systems Engineering University of Nebraska Lincoln Lincoln Nebraska USA

Faculty of Biomedical Engineering Department of Health Care and Population Protection Czech Technical University Prague Czech Republic

Faculty of Physical Education and Sport Sport Sciences Biomedical Department Charles University Prague Czech Republic

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