A variable-view arthroscope or similar instrument (endoscope, etc.) includes a housing tube with an input end. The housing tube contains an input assembly and a portion of a light relay assembly. A control varies the position of the input assembly to change the viewing position of the arthroscope. In certain embodiments, the control uses external master magnets that rotate around an axis orthogonal to the longitudinal axis of the housing to drive internal slave magnets magnetically. This permits the housing to be sealed completely. In certain embodiments, a cam-axle assembly translates the rotational motion of the internal slave magnets to linear motion that drives a push rod that manipulates the input assembly.