An instrument sterile adapter for coupling a surgical instrument and an instrument carriage includes an adapter control surface that extends control features of a control surface of the instrument carriage and receives an instrument control surface of the surgical instrument. A shaft receiving slot is positioned in the adapter control surface to receive an elongate tube of the surgical instrument when the adapter control surface receives the instrument control surface of the surgical instrument. The elongate tube may couple a proximal control mechanism of the surgical instrument to an end effector. The instrument sterile adapter may include a convex curved surface substantially perpendicular to and facing the adapter control surface to receive a corresponding concave curved surface on the instrument control surface. A bullet portion on the convex curved surface may engage a bullet receiving feature in the corresponding concave curved surface on the instrument control surface.