Publications

• The findings of this systematic review suggest that MyotonPRO® is a practical and reliable tool for assessing stiffness characteristics of healthy lower extremity tendons, particularly the Achilles and patellar tendons. Its portable and non-invasive characteristics allow repeated measurements and may support tendon assessment in clinical and sports settings.

Background: Accurate quantification of tendon stiffness is essential for monitoring injuries, rehabilitation, and athletic performance. Ultrasound-based methods are informative, but costly and operator-dependent. The handheld MyotonPRO® has emerged as a low-cost alternative, but its psychometric profile across human tendons remains unclear. Therefore, this systematic review synthesized the current evidence on the validity and reliability of MyotonPRO® in assessing tendon stiffness.

Methods: In accordance with PRISMA, systematic searches of PubMed, Web of Science, and Scopus were conducted in April 2026. Peer-reviewed studies in English that reported intra- or inter-rater reliability and/or criterion validity were included in this review. Methodological quality was appraised using the COSMIN and QAREL checklists for reliability studies and QUADAS-2 for validity studies.

Results: Nineteen studies met the inclusion criteria (Achilles = 15, patellar = 6, quadriceps = 1). Intra-rater intraclass correlation coefficients (ICCs) ranged from 0.74 to 0.96 for the Achilles tendon, 0.51 to 0.99 for the patellar tendon, and 0.92 to 0.94 for the quadriceps tendon; inter-rater ICCs were similarly high. The standard errors of measurement were 3.95-105.5 N/m, indicating good absolute reliability. Validity was assessed in three achilles tendon studies, with inconsistent findings : one reported a moderate correlation (r= 0.538), one construct validity, and one poor agreement ( ICC= 0-0.09).

Conclusion: MyotonPRO® demonstrates moderate-to-excellent reliability for assessing Achilles, patellar, and quadriceps tendon stiffness, although evidence for the quadriceps tendon is limited. Current validity evidence is restricted to the Achilles tendon and remains inconsistent. Further high-quality studies using standardized protocols and reference methods are needed to establish its validity.

Keywords: Achilles tendon, elasticity, reliability of results, tendons, validity of results

The studies reviewed in this systematic review have shown that the reliability of stiffness measurements with MyotonPRO® is mostly good-to-excellent (ICC >0.80), regardless of the experience of the assessor, sex or physical activity level of the participants, tendon assessed, joint angle and assessment site assessed for the same tendon, and the reliability analysis method utilized (intra-and inter-rater reliability). The findings of the present systematic review indicate that MyotonPRO® appears to be a reliable tool for measuring lower limb tendon stiffness in healthy participants. However, current evidence regarding validity remains limited and requires further investigation using standardized validation approaches.