"For a better understanding of the present invention, a detailed description will be given below with reference to accompanying drawings, in which: FIG. 1 is an exploded perspective view showing an embodiment of the joint mechanism of the invention as it is applied to knee prosthesis; FIG. 2 is a rear view of the same as it is assembled; FIG. 3 is a side elevation of the same; FIG. 4 is a view illu" . . . .