Abstract This article presents an exploratory study investigating the kinematic variations made by transtibial amputees during gait with knee hyperextension. Other authors have studied other abnormal amputee gait patterns like circumduction or vaulting. The within-subject study involved 20 participants and used the MVN Awinda Motion Capture System to record kinematic variables during gait cycles. Knee hyperextension was induced by using a 3D-printed outsole placed on the prosthetic foot in order to restrict the ankle dorsi-flexion angle. The condition was verified by inspecting the kinematic curve of this joint in the sagittal plane. After this inspection, two groups were identified based on flexion-extension angles during mid-stance: one group had a constant flexion-extension angle during this sub-phase and the other one had a fluctuating angle. Differences between control and hyperextension trials were found in ankle, knee, and hip joints. Group 1 showed higher values for ankle flexion on the healthy limb during all gait events in the control trial and higher hip abduction and shoulder flexion during all gait events during hyperextension trials. Group 2 presented higher values for the healthy knee abduction during heel strike and load response and hip abduction on the amputated side during load response and terminal extension during knee hyperextension trials. Future studies should consider using physiological information such as electromyography to deepen understanding of this abnormal gait pattern. These findings have important implications for early diagnosis and prevention of future difficulties resulting from knee hyperextension in transtibial amputees. The presented findings can be implemented in the creation of automated gait pattern detection algorithms as well.