Chronic rupture of the Achilles tendon (AT) is a surgical challenge and has effects on the gait. The purpose of this study was to evaluate the kinetic and kinematic parameters of the ankle joint in patients with AT rupture operated using a free semitendinosus tendon graft. Thirteen patients were analyzed 6 and 12 months after surgery in a force platform, while the movements were recorded by six infrared cameras. The kinematic variables analyzed included speed, cadence, step length, percentage of stance phase, and range of movement (ROM) of the ankle joint in the sagittal and frontal planes. Kinetic data were obtained by joint movement in different phases of the gait cycle. Functional assessment was performed using the American Orthopaedic Foot and Ankle Society (AOFAS) score. The patients showed a significant increase (P=0.0215) in AOFAS from 68.5 (+/- 18.7) to 85.2 (+/- 18.0). Speed, cadence, and length of step of the four groups (1A, 1B, 2A, 2B) were lower than the control group (group 3), and the percentage in stance phase was higher for the nonoperated foot 6-month group (1B) compared to the control group (group 3). For the kinematic data, the ROM of the ankle in stance phase increased from 6 to 12 months showing an effect of time between four groups (1A, 1B, 2A, 2B). During swing phase, the ankle ROM was lower in the operated side (effect of side, P=0.0255) and groups 1A and 2A demonstrated statistical differences when compared with the control group (group 3) (P=0.0240 and P=0.0414, respectively). ROM of inversion and eversion presented effect of time among the same groups (P=0.0059) cited before. There were no differences in kinetic data between groups. This study showed close proximity between the control group and the operated group. Furthermore, improvement was shown when comparing the 6 and 12 months postsurgery periods. The surgical procedure is therefore helpful for the patient and few changes were present in gait and ankle biomechanics.373291297