Abstract: A flexing apparatus including first and second straps to encircle the body above and below a joint, pivotable links between the straps to maintain alignment between them and piston and cylinder assemblies extending between the straps. Adjustable bleed valves in the cylinder ends provide calibrated leakage to present resistance to flexion and extension of the joint. An air supply and control are attached to the cylinder ends to provide controlled power flexion and extension of the joint for therapy, including a compressor, air filtering, regulating and lubricating devices, a two position solenoid operated valve and an electrical timing and switching circuit for energizing the solenoid.