An implant is insertable in the joint space to separate bones of the joint. The implant has two endplates each configured to engage a separate articulating bone of the joint, and a threaded member positioned between the two endplates and configured to increase the space between the two endplates when the threaded member is rotated. A rotatable gear is engaged with the threaded member, and is engageable with a rotating gear of a connected implantation tool, so that rotation of the gear on the tool causes rotation of the threaded member and expansion of the implant to separate the bones. Connector portions on the tool and the implant may be rotated together to securely engage the implant and the tool so that the gears of the tool and the implant can be rotated using an actuator outside of the body, when the implant is inside the body.