An armrest assembly is provided for adjusting an armrest of a seating unit in three degrees of motion. The armrest assembly includes an angle-adjustment mechanism that allows the armrest to pivot and to translate forward, and a lift mechanism that enables vertical articulation of the armrest. The angle-adjustment assembly includes a pivot bracket with a downwardly disposed pin and a shuttle with an arcuate slot to receive the pin. The arcuate slot includes contoured walls that form detents for restricting movement of the pin, thereby restraining rotation of the shuttle, with respect to the pivot bracket, to predefined angular positions. The lift mechanism includes a rack with ride element(s) extending therefrom and locking teeth, and a control bar with track(s). An upward manual actuation of the control bar causes the track to shift laterally and retract the locking teeth, via interaction between the track(s) and ride element(s), respectively.