Synthetic limbs are able to mimic the look of the original human limb. They require charging overnight for use during the day.
Detective John Kennex was fitted with a synthetic leg after his leg was blown off during a botched raid. He has no feeling in the synthetic limb and requires calibration in order for the leg to work correctly.
In "Arrhythmia", John was pressured into donating to a synthetic limb fund for children whose families can't afford the technology.