Medical systems and methods for making and using medical systems are disclosed. Example medical systems may include an atherectomy system configured to engage and remove plaque from walls in vessels of a vascular system. The atherectomy system may include a drive shaft, a rotational tip coupled to an end of the drive shaft, a drive mechanism coupled to the drive shaft to rotate the rotational tip, a control unit configured to control operation of the drive mechanism, and a knob assembly configured to facilitate longitudinal movement of the drive shaft, the rotational tip, and/or the drive mechanism. In some cases, the knob assembly may be configured to initiate adjustment of a mode of the drive mechanism in response to actuation of an actuator in the knob assembly.