A sealed joint assembly includes an outer joint part (3) with outer ball tracks (9), an inner joint part (4) with inner ball tracks (10), torque transmitting balls (6) which are guided in pairs of tracks and held in a cage (7) with cage windows (8). A sleeve (16) is connected to the inner joint part (4) and is coaxially arranged thereto. A sealing mechanism (12) with an annular cap (13) is fixed to the outer joint part (3) and includes a sealing diaphragm (15) with an outer collar (18) connected to the annular cap (13) and an inner collar (19) sealingly connected to the sleeve (16). A securing ring (20) fixes the inner collar (19) on the sleeve (16). The sleeve (16) has an annular groove (33) which is engaged by the sealing diaphragm (15) by an inner annular bead (32) formed on the inner collar (19).