Abstract: The present invention relates to the field of wearable robotic devices that physically interact with humans, and in particular refers to a wearable exoskeleton, in particular for the upper limb. The invention refers to an electro- or magneto-rheological fluid type semi-active joint purposely conceived to be used to make the exoskeleton. It comprises a first body and a second body, slidably coupled to each other, with a “flow mode” rotating configuration, which allows to have a fluid flow moved by a pressure gradient induced by the circular movement of a piston in a chamber, with constructive simplicity and decrease of wear.