Background At present, there is no validated patient-reported outcome measure (PROM) for patients with medial tibial stress syndrome (MTSS).

Aim Our aim was to select and validate previously generated items and create a valid, reliable and responsive PROM for patients with MTSS: the MTSS score.

Methods A prospective cohort study was performed in multiple sports medicine, physiotherapy and military facilities in the Netherlands. Participants with MTSS filled out the previously generated items for the MTSS score on 3 occasions. From previously generated items, we selected the best items. We assessed the MTSS score for its validity, reliability and responsiveness.

Results The MTSS score was filled out by 133 participants with MTSS. Factor analysis showed the MTSS score to exhibit a single-factor structure with acceptable internal consistency (α=0.58) and good test–retest reliability (intraclass correlation coefficient=0.81). The MTSS score ranges from 0 to 10 points. The smallest detectable change in our sample was 0.69 at the group level and 4.80 at the individual level. Construct validity analysis showed significant moderate-to-large correlations (r=0.34–0.52, p<0.01). Responsiveness of the MTSS score was confirmed by a significant relation with the global perceived effect scale (β=−0.288, R²=0.21, p<0.001).

Conclusions The MTSS score is a valid, reliable and responsive PROM to measure the severity of MTSS. It is designed to evaluate treatment outcomes in clinical studies.