Patient support and positioning system for continuous passive motion (CPM) machines comprising a fully adjustable chair to which is attached a horizontal telescoping arm having a coupling member for fastening the vertical stand of a CPM machine thereto. The chair has full adjustment in all axes: rotation around a vertical center axis; vertical height adjustment; fully adjustable seat back, both fore-and-aft and vertically for proper lumbar support; and tilt of the seat. The telescoping arm is lockably adjustable in length to provide proper center-to-center distance between the center post of the chair and the CPM machine support. The arm further includes a downward vertical step member at its outboard CPM machine connecting end to permit proper vertical alignment of the CPM machine for users having a short torso. The arm also provides a support for a CPM power supply/control unit, and has means for securing the power cord out of the way off the floor. The invention permits support of the patient with a full range of adjustment so that the patient can have proper positioning for selected exercise of the selected extremity in flexion/extension, forward flexion/extension internal/external rotation, supination/pronation and the like.