This paper deals with the nonlinear control of a lower limbs isokinetic rehabilitation device based on a Takagi- Sugeno modeling. A Parallel Distributed Compensation control law is used to stabilize the closed-loop system in the whole operational space. The human force applied to the device’s arm is considered as an external disturbance to the system dynamics. To attenuate this disturbance, an H∞ criterion is considered and classical stability conditions were adapted for a class of external perturbed TS model. The voluntary control of the movement by the patient is finally proposed with the use of a discrete state machine.