A user control knob retention system includes a nut (20) which has a base (25). The base includes two opposing nut end faces (23a, 23b), and a threaded bore (21) aligned with a base central axis (29). A wall (27) extends transversely from a first one of the nut end faces. The wall defines an inner surface (42) which comprises a circular arc coaxial with the central axis. The wall extends at least partially around a circumference of the base to define a capture space (26). An insert (30) rotatably retained within the capture space includes a body having a cylindrical shape. A retention barb (34) disposed on an outer cylindrical surface of the insert is configured for engaging an interlocking element (54) formed on an interior bore (58) of a user control knob (50).