A system includes an adjustable implant configured for implantation internally within a subject, the adjustable implant having a permanent magnet configured for rotation about an axis of rotation, the permanent magnet operatively coupled to a drive transmission configured to alter a dimension of the adjustable implant. The system further includes an external adjustment device configured for placement on or adjacent to the skin of the subject comprising at least one magnet configured for rotation, the external adjustment device further comprising a motor configured to rotate the at least one magnet, whereby rotation of the at least one magnet of the external adjustment device effectuates rotational movement of the permanent magnet of the adjustable implant and alters the dimension of the adjustable implant. The system includes drive control circuitry configured to drive the motor of the external adjustment device to achieve a target dimension of the adjustable implant.