This text provides the reader an understanding of the mechanics of the joints with the help of diagrams rather than text. The commentaries are short (on double page spreads); the quality, clarity and simplicity of the drawings and diagrams are such that they could be understood without any verbal explanation. The drawings are unusually clear: everything which could hinder understanding has been removed and one feels that the author has foreseen the difficulties which the student could encounter. Each time a problem arises it is explained by a diagram which, though simplified, is extremely clear.