Which of the following correctly states the classification of the first carpometacarpal joint at the base of the thumb?

• A Plane synovial joint between trapezium and first metacarpal
• B Condylar synovial joint allowing movement in two axes
• C Pivot synovial joint permitting opposition only
• D Saddle synovial joint between trapezium and first metacarpal ✓

Explanation

The reciprocally concavoconvex surfaces of the trapezium and the base of the first metacarpal form a classic saddle (sellar) joint, granting movements in two axes: flexion-extension, abduction-adduction, and their combination as opposition, the hallmark of the human thumb. Its wide range depends on the lax capsule, which is reinforced by anterior and posterior oblique ligaments. Plane joints such as the second and third carpometacarpal joints permit only gliding, explaining the thumb's unique mobility.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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