Disclosed herein are lock mechanisms configured for locking and unlocking rotation of a driver and a driven gear system in implantable distraction and compression systems, and implantable medical devices and implantable distraction and compression systems including such lock mechanisms. The lock mechanisms include a keeper that is configured to move from a locked position to an unlocked position in response to a rotation of the driver, wherein, in the locked position, the keeper is configured to resist rotation of the driven features and the driver under a load on the driven features, and in the unlocked position, permits rotation of the drive gear and the driver.

Disclosed herein are lock mechanisms configured for locking and unlocking rotation of a driver and a driven gear system in implantable distraction and compression systems, and implantable medical devices and implantable distraction and compression systems including such lock mechanisms. The lock mechanisms include a keeper that is configured to move from a locked position to an unlocked position in response to a rotation of the driver, wherein, in the locked position, the keeper is configured to resist rotation of the driven features and the driver under a load on the driven features, and in the unlocked position, permits rotation of the drive gear and the driver.