A hyperextension orthopaedic brace (10) comprising a frame structure composed of a pair of upper sternal bars (12) with substantially horizontal development and mutually adjustable, two pairs of lateral uprights (26, 28) with substantially vertical development, each comprising an upper lateral upright (26) and a lower lateral upright (28) mutually adjustable, as well as a substantially horizontal pelvic band (34) for connecting the pairs of lateral uprights (26, 28), as well as a rear belt (36) for the application to the trunk, constrainable at the opposite ends thereof to the pairs of lateral uprights (26, 28), has pairs of lateral uprights (26, 28) constrained to the pelvic band (34), at the ends thereof, by means of a spherical joint (40) comprising a monolithic body (42), made in a single piece of thermoplastic material and stably constrained at an end of the lower lateral upright (28), wherein the monolithic body (42) comprises a spiral spring (46), made in a single piece with the monolithic body by means of a lamina connected at a peripheral end thereof in a single point of the inner wall of a central opening (45) and wound in a spiral, in clockwise or counterclockwise direction, towards the centre of the same, identifying, at the opposite end thereof, a central button (47) provided with anti- rotational stable engagement means with the pelvic band (34).
