An orthosis for treating muscle disorders of the elbow has a body made in one piece from a semi-rigid material. The body includes a distal portion, a proximal portion, and a back joining strap. In the unstressed state, the relative position of the distal and proximal portions maintains the wrist in an extended state. The joining strap is deformable such that when pressure is exerted downward on the palm support, the joining strap is deformed to enable the pivotal movement of the distal portion with respect to the proximal portion about a transverse articulation axis parallel to the flexion-extension axis of the wrist. When pressure is released, the body returns to the unstressed state due to resilience. The distal portion is arranged to pivot with respect to the proximal portion about the articulation axis while assisting the extensor muscles of the wrist.
