The invention relates to a backrest assembly (1, 100, 200) for a wheelchair with a backrest frame (20, 120, 220) pivotally connected to a seat or seat frame (10), a carrying means (30, 130, 230) provided by or attached to the backrest frame (20, 120, 220), a rotating means (40, 40', 140, 240) rotatable secured to the carrier means (30, 130, 230), a first sliding means (50, 150, 250) slidable connected to the backrest frame (20, 120, 220) on the rear side of the backrest assembly (1, 100, 200) and connected to the rotating means (40, 40', 140, 240) via a first mechanical link, a second sliding means (60, 60',160, 260) slidable secured to the backrest frame (20, 120, 220) on the front of the backrest assembly (1, 100, 200) and connected to the rotating means (40, 40', 140, 240) via a second mechanical link, and an actuator (70, 170, 270) for adjusting the backrest assembly (1, 100, 200) between an upright and reclined position with a recline angle, the recline angle driving the second sliding means (60, 60',160, 260) to perform a sinusoidal movement.
