A sealing assembly for insertion between first and second mechanical elements subjected to offset positioning, including a reinforcement ring and at least one elastomeric sealing element in which the reinforcement ring is at least partially embedded, the sealing element including an annular membrane shaped as a truncated-cone sleeve and free from the reinforcement ring, which membrane obliquely extends to protrude from the reinforcement ring, towards a symmetry axis of the sealing assembly and ends with at least one annular sealing lip intended to slidingly cooperate with the first mechanical element; the membrane has, in radial direction, a relatively thin thickness, thinner than that of the at least one sealing lip, so as to be highly flexible, and a plurality of stiffening ribs formed with the membrane, which extend in the axial direction, parallel to one another, spaced apart from one another to form longitudinally extending radial projections on the membrane.