A forceps includes a housing, a shaft assembly, an end effector assembly, and a waveguide assembly. The housing has one or more transducers that generate a mechanical vibration in response to energy transmitted thereto from an energy source. The shaft assembly extends from the housing and includes one or more articulating and clamping members and a longitudinal axis defined therethrough. The end effector assembly is disposed at a distal end of the shaft assembly and includes a pair of opposing jaw members pivotable between approximated and unapproximated configurations in response to movement of the one or more clamping members. The articulating members articulate the jaw members relative to the longitudinal axis of the shaft assembly. The waveguide assembly is positioned within the shaft assembly and receives the mechanical vibration generated by the transducer. The waveguide assembly is positionable within one or both of the jaw members.