A bone screw having a head and a shank. The shank having a ball thereon and the head having a socket for receiving the ball. The ball being externally threaded and the chamber communicating with the exterior of the head through a threaded bore. The ball being threadably received through the bore and being swivelable in the chamber after passing through the bore. The bone screw including at least one set screw that operably engages the ball to lock the head in position relative to the shank.