This book describes the anatomy and biomechanics of the trapeziometacarpal joint and explains the pathogenesis and treatment of trapeziometacarpal joint osteoarthritis, also known as rhizarthrosis. The discussion of treatment sets out both conservative and surgical approaches, clearly explaining the indications for the various options, as well as their advantages and disadvantages. The trapeziometacarpal joint is a phylogenetically recent articulation that permits the pinching movements of the index finger and thumb so important in daily activities. Degenerative disease involving the trapeziometacarpal joint is an important disabling condition that affects predominantly females over 50 years old.