A post joint assembly and a method are provided. The assembly includes an upper cup member having a flat top wall, a tubular wall, a flange portion, and a threaded stud. The assembly further includes a lower cup member having a parabolic dish portion, a tubular portion, and a beaded edge portion. An outer surface of the parabolic dish portion is disposed against an inner surface of the flange portion of the upper cup member such that the threaded stud extends through a first hole in the lower cup member. The assembly further includes a tensioner cup having a second hole with the threaded stud extending therethrough. The assembly further includes a nut threadably coupled to the threaded stud such that the nut urges the tensioner cup against the lower cup member, and further urges the lower cup member against the upper cup member.