Publications

• MyotonPRO shows potential as a useful tool to assess regional mechanical properties of the patellar tendon under non-weight-bearing and weight-bearing conditions.
• This study found increases in patellar tendon stiffness in the medial region during non-weight-bearing flexion and in the proximal-central region during decline squats. These findings highlight the importance of region-specific mechanical assessment in understanding the pathophysiology of patellar tendinopathy.
• Assessment of regional tendon mechanics using MyotonPRO may be valuable for monitoring tendon status and serving as an outcome measure.

Background: Patellar tendinopathy commonly affects the central and medial proximal portions of the patellar tendons, suggesting regional variations in its mechanical properties. Nevertheless, the in vivo regional mechanical characteristics remain unclear. In this study, we examined how patellar tendon stiffness changes regionally during non-weight-bearing and weight-bearing movements performed under different loads.

Methods: Twenty healthy men participated. Tendon stiffness was assessed in nine regions (3 × 3 grid) with a myotonometer at knee-flexion angles of 30° and 60° in supine, squatting, and decline-squatting positions. The reliability of multi-point patellar tendon stiffness measurements using a myotonometer was evaluated. Two-way repeated-measures analysis of variance (ANOVA) compared stiffness between knee angles and regions for each task. When interactions were identified, one-way repeated-measures ANOVA or the Friedman test with Bonferroni post-hoc corrections was applied to explore stiffness changes attributable to knee flexion.

Results: Patellar tendon stiffness measurements demonstrated a moderate to high reliability in both non-weight-bearing and weight-bearing conditions (intraclass correlation coefficient range: 0.553–0.958). In the supine position, stiffness increases were larger in the medial than in the lateral region at all measurement levels (p < 0.05). Squatting elevated stiffness across all regions without significant regional disparities (mean difference across regions: 80.8 N/m). Conversely, during decline squats, the proximal-central region exhibited greater stiffness increases than did the proximal-lateral region (proximal-central: 98.5 N/m, proximal-lateral: 40.0 N/m, p < 0.05).

Conclusion: These non-uniform regional adaptations may partly clarify why patellar tendinopathy preferentially develops in specific areas. Region-specific stiffness responses can be used to inform exercise selection and load management strategies.

When knee flexion increased from 30° to 60°, tendon stiffness rose in the medial region during non-weight-bearing flexion and in the proximal-central region during decline squats, whereas level squats elicited no regional differences in patellar tendon stiffness. Because the decline-squat posture mirrors the jump-landing position adopted by individuals with patellar tendinopathy, the regional-specific stiffness changes observed here may help explain the predilection for lesions in the medial and central proximal tendon. Accordingly, examining regional mechanical properties may yield novel insight into the pathophysiology of patellar tendinopathy. From a clinical perspective, identifying region-specific stiffness responses to different loading conditions may support exercise selection and load management. MyotonPRO can be a practical and non-invasive method of regional tendon assessment in clinical settings.