Trapezium

Function

Saddle-shaped base of the thumb. Its reciprocally saddle-shaped joint with the first metacarpal gives the thumb its unique human opposition — the joint that made tool-making possible.

Landmarks

• Saddle-shaped facet
• Tubercle and groove (flexor carpi radialis)

Articulations (joints)

• First metacarpal (saddle joint)
• Scaphoid
• Trapezoid

Clinical relevance

Osteoarthritis of the trapeziometacarpal joint (basal thumb arthritis) is the most disabling common hand arthritis; grind test elicits crepitus.