Abstract: A surgical instrument is provided for performing operations on joints, comprising an elongated hollow body; an elongated tube fixedly connected at one end to the body and adapted for insertion into a joint at a selected location; a manipulator shaft axially movable in the tube and in the body; a substantially planar cutting member on one end of the shaft; and member manipulatable by the fingers to move the shaft between a first position in which the cutting member is withdrawn within the tube and a second position in which the cutting member is extended beyond the end of the tube; the tube having a rounded closed end with a slot therethrough through which the cutting member is extended and withdrawn and effective to guide the cutting member during such movement and to restrain the cutting member against rotation during such movement and while cutting.