An acetabular reamer comprising: a body defining a rotation axis about which the acetabular reamer is rotatable a reaming element movable between a reaming element inner position and a reaming element outer position relative to the body an actuator for moving the reaming element between the reaming element inner and outer positions and a reaming element lock configurable between a locked configuration and an unlocked configuration. In the unlocked configuration, the reaming element is freely movable by the actuator between the reaming element inner and outer positions. In the locked configuration, the reaming element lock prevents the reaming element from moving relative to the body. In use, when the reaming element lock is in the locked configuration and reaction forces are exerted onto the reaming element, a larger portion of the reaction forces is transmitted to the body than to the actuator.
