Test–retest Reliability of Biomechanical Measures and Clinical Pain Outcomes in Runners with Medial Tibial Stress Syndrome (MTSS)

Medial tibial stress syndrome (MTSS) is a common overuse injury in runners, leading to pain and reduced training capacity. Reliable assessment of biomechanical and clinical outcomes is essential to distinguish true clinical change from measurement error and for guiding rehabilitation and return-to-running decisions. However, evidence for the reliability of commonly used measures in MTSS is limited. # Purpose To determine the test-retest reliability and minimal detectable change (MDC) of common biomechanical and clinical outcomes in runners with MTSS. # Study design Test-retest reliability study. # Methods Twenty-two runners with MTSS were assessed twice, three days apart, by the same examiner. Biomechanical outcomes included center of pressure (COP) trajectory during running and cross-sectional area (CSA) and strength of the flexor hallucis longus (FHL) muscle. Clinical outcomes included linear pain distance on palpation along the posteromedial tibial border, and pain level reported using a visual analog scale (VAS). Paired t-tests were used to analyze the differences between sessions. Intraclass correlation coefficients (ICC_3,k) were calculated to assess reliability. The standard error of measurement (SEM), the MDC and the Bland-Altman plot were calculated. # Results No significant differences between sessions were observed for any outcome. Test-retest reliability was good to excellent for COP (ICC_3,1=0.92), linear pain distance on palpation along the posteromedial tibial border (ICC_3,1=0.94), CSA (ICC_3,3=0.82), and FHL strength (ICC_3,3=0.88). SEM and MDC value were 0.86% and 2.38% for COP, 0.77 cm and 2.12 cm for linear pain distance on palpation along the posteromedial tibial border, 0.23 cm² and 0.63 cm² for CSA, and 0.54 kg and 1.49 kg for FHL strength. The Bland-Altman plot shows the agreement of all variables. # Conclusion Common biomechanical and clinical outcomes in runner with MTSS demonstrated good to excellent test-retest reliability. The established MDC values provide reference thresholds for interpreting meaningful change and support evidence-based rehabilitation and return-to-running protocols. # Level of evidence Level 3.