Connection joint for adjusting the inclination between a first frame and a second frame of a structure, such as a sun lounger, comprising: - a fixed half-joint, suitable to be attached to the first frame of the sun lounger, - a mobile half-joint, suitable to be connected to the second frame of the sun lounger, where such fixed and mobile half-joints have respective mutual coupling portions (16, 17) around which jointly delimit a joint seat in which an adjustment mechanism of the angular position of the mobile half-joint in relation to the fixed half-joint is housed, said half-joint adjustment mechanism comprising: - a fixed crown gear, integral with the coupling portion of the fixed half-joint, - a mobile ring nut, integral in rotation with the mobile half-joint, said mobile ring nut being provided with an annular counter-gear suitable to engage in the fixed crown gear to identify a plurality of angular coupling positions between said mobile ring nut and said fixed crown gear, - a spacer ring positioned around the fixed crown gear, said spacer ring having a cam profile which the mobile ring nut engages on, in said cam profile a first engagement portion with the mobile ring nut being made, wherein mobile ring nut snap engages the fixed crown gear in steps and drags the spacer ring in rotation around the fixed crown ring, a second engagement portion with the mobile ring nut, wherein the mobile ring nut is disengaged from the fixed crown gear and drags the spacer ring in rotation around the fixed crown gear, and a third engagement portion with the mobile ring nut, wherein the mobile ring nut is disengaged from the fixed crown gear and is free to rotate in relation to the spacer ring, the spacer ring and the fixed half-joint being fitted with stop means (310, 40) to block the rotation of the spacer ring in at least one end-stroke position of the second frame, so as to allow the passage of the mobile ring nut from the engagement position with the first portion to the engagement position at least with the second engagement portion with the spacer ring, - elastic ring-nut stressing means, said elastic means acting axially on the mobile ring nut in the direction of engagement with the fixed crown gear and being suitable to allow a controlled reversing of the mobile ring nut for the stepped rotation on the fixed crown gear and for the passage of the mobile ring nut from the first to the second and from the second to the third engagement position with the spacer ring. - a fixed half-joint, suitable to be attached to the first frame of the sun lounger, - a mobile half-joint, suitable to be connected to the second frame of the sun lounger, - a fixed crown gear, integral with the coupling portion of the fixed half-joint, - a mobile ring nut, integral in rotation with the mobile half-joint, said mobile ring nut being provided with an annular counter-gear suitable to engage in the fixed crown gear to identify a plurality of angular coupling positions between said mobile ring nut and said fixed crown gear, - a spacer ring positioned around the fixed crown gear, said spacer ring having a cam profile which the mobile ring nut engages on, in said cam profile a first engagement portion with the mobile ring nut being made, wherein mobile ring nut snap engages the fixed crown gear in steps and drags the spacer ring in rotation around the fixed crown ring, a second engagement portion with the mobile ring nut, wherein the mobile ring nut is disengaged from the fixed crown gear and drags the spacer ring in rotation around the fixed crown gear, and a third engagement portion with the mobile ring nut, wherein the mobile ring nut is disengaged from the fixed crown gear and is free to rotate in relation to the spacer ring, the spacer ring and the fixed half-joint being fitted with stop means (310, 40) to block the rotation of the spacer ring in at least one end-stroke position of the second frame, so as to allow the passage of the mobile ring nut from the engagement position with the first portion to the engagement position at least with the second engagement portion with the spacer ring, - elastic ring-nut stressing means, said elastic means acting axially on the mobile ring nut in the direction of engagement with the fixed crown gear and being suitable to allow a controlled reversing of the mobile ring nut for the stepped rotation on the fixed crown gear and for the passage of the mobile ring nut from the first to the second and from the second to the third engagement position with the spacer ring.