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An anatomical and biomechanical study of the stabilizing ligaments of the thumb trapeziometacarpal joint was conducted on 32 hand specimens. Five main ligamentous structures could be identified. The mechanical properties (in particular, strength) of the five ligaments using a strain-rate failure test were determined and evaluated quantitatively. The maximum tensile strength of each ligament was correlated with the condition of the trapeziometacarpal articular cartilage. In studying the anterior oblique ligament, maximum strength decreased from Grade 0 to Grade 1 by 51%. With the first intermetacarpal ligament, the drop from Grade 1 to Grade 2 was 53%. With the posterior oblique ligament, the decrease was closely related to the grade of the deterioration of the trapeziometacarpal articular surface. These three ligaments also significantly decreased in strength with age. Our results may suggest that the anterior oblique ligament, intermetacarpal ligament and posterior oblique ligament play a large role in stabilizing the trapeziometacarpal joint and that the decrease in their strength is related to the pathogenesis of trapeziometacarpal osteoarthritis.