CMC Jt.

Question 1

Trapezium is CONCAVE in the plane of CMC abduction/adduction

Answer 1

During CMC abduction or adduction (in a direction perpendicular to the palm), the metacarpal rolls and glides in opposite directions.

Question 2

Trapezium is CONVEX in the plane of CMC flexion/extension

Answer 2

During CMC flexion or extension (in a direction parallel to the palm), the metacarpal rolls and glides in the same direction.