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Background: Despite anecdotal evidence linking overpronation to the onset of Achilles tendinopathy (AT), there is little conclusive evidence of a particular movement pattern of the lower extremity associated with this injury. Therefore, the objective of the present study was to observe differences in the kinematic profiles of healthy runners (CON) and runners with mid-portion Achilles tendinopathy (ATG). Materials and Methods: In this cross-sectional analysis, 48 male height and weight matched subjects were invited to participate: 27 with mid-portion Achilles tendon pain and 21 asymptomatic controls. Subjects underwent lower extremity clinical examination, then ran barefoot for 10-trials at a self-selected pace. A 3D motion capture system analysed tri-plane kinematic data for the lower extremity. Results: The ATG displayed significantly greater sub-talar joint eversion displacement during mid-stance of the running gait (13 ± 3 degrees vs. 11 ± 3 degrees; p = 0.04). Trends were observed such that the ATG showed lower peak dorsiflexion velocity (300 ± 39 degrees/s vs. 330 ± 59 degrees/s; p = 0.08) and greater overall frontal plane ankle joint range of motion (45 degrees ± 7 vs. 41 degrees ± 7; p = 0.09). Conclusion: We found an increase in eversion displacement of the sub-talar joint in runners with Achilles mid-portion tendinopathy. Based on the findings from this study, there is evidence that devices used to control sub-talar eversion may be warranted in patients with Achilles mid-portion tendinopathy who demonstrate over-pronation during mid-stance of the running gait