Abstract: The hip-or shoulder-joint endoprosthesis has a stem (10) and a ball head (20) that has an arched top side (21) and a closed underside (22). The longitudinal axis of the stem (10) forms an angle of at most 30° with the axis of the ball head (20). The stem (10) tapers with an overall aperture angle in the range of 5 to 30°. The ball head (20) has the shape of a sphere section of less than a hemisphere. The length of the stem (10) is less than the diameter of the ball head (20). The longitudinal axis of the stem (10) can coincide with the axis of the ball head (20).