The human hand has how many degrees of freedom (DOFs)?

• A. 11
• B. 44
• C. None of these
• D. 22

Answer: (D)

This question hinges on how many independent motions each joint in the hand can perform. The four fingers contribute 16 DOFs: each finger’s MCP joint has flexion/extension and abduction/adduction (2 DOFs), while the PIP and DIP joints each provide one DOF (flexion/extension). So for four fingers: 4 DOFs per finger × 4 fingers = 16 DOFs.

The thumb adds more freedom because its base joint, the carpometacarpal joint, is especially versatile. It has three independent motions: flexion/extension, abduction/adduction, and axial rotation that enables opposition. The thumb’s MCP joint provides two DOFs, and the thumb’s interphalangeal joint provides one DOF. So the thumb contributes 3 + 2 + 1 = 6 DOFs.

Total DOFs = 16 (fingers) + 6 (thumb) = 22. The extra DOF at the thumb’s base (opposition/rotation) is what pushes the count from a lower number to 22. Some sources count only two DOFs for the thumb CMC and would arrive at 21, but including the axial rotation for opposition yields 22.