A prosthetic or orthotic device can include at least one device portion and a joint portion for providing for the at least one device portion to pivot between flexion and extension movements relative to another adjacent device portion or an adjacent limb segment of a user. In some embodiments, a prosthetic or orthotic device can include a compliant transmission assembly in operational communication with the joint portion. The compliant transmission assembly can include a compliant member and a pivot. The pivot can be interposed between the compliant member and the joint portion. In some embodiments, the compliant member absorbs energy when a torque is applied.