Mechanisms for a control knob or other interface device providing additional degrees of freedom for the knob. One embodiment provides a rotatable knob moveable also in a lateral plane approximately perpendicular to the axis of rotation. A mechanism providing the lateral motion can include a gate member and a plunger member that engages grooves in the gate member. A rotational sensor detects a rotational position and a lateral sensor can detect a lateral position of the knob. Another embodiment provides an actuator that includes a shaft that is coaxial with the axis of rotation and which can be moved linearly along the axis of rotation with respect to actuator housing to accommodate linear motion of the knob. In another embodiment, a gear assembly including two interlocked gears is provided to transmit rotational motion from the knob to the sensor, and the interlocked gears translate with respect to each other when the knob is translated along the rotational axis.