Background: Individual treatment selection has been proposed as the key to optimized treatment. The purpose was to investigate if treatment selection using the individualized treatment algorithm Copenhagen Achilles Rupture Treatment Algorithm (CARTA) differs between patients treated as usual regarding gait dynamics and tendon elongation. Methods: The patients were randomized to one of three parallel groups: 1) intervention group: participants treated according to CARTA, 2) control group: participants treated non-operatively, 3) control group: participants treated operatively. The primary outcome was ankle peak power during push off during walking at 12 months. Results: 156 patients were assessed for eligibility. 21 were allocated to the intervention group, and 20 and 19 to the control groups. The results indicated no statistically significant differences between the intervention group and the control groups. Conclusions: Individualized treatment selection based on CARTA did not demonstrate less affected gait dynamics or less tendon elongation than patients treated as usual.