Which joint is primarily capable of flexion (bending) and extension (straightening)?

Which joint is primarily capable of flexion (bending) and extension (straightening)?

• A. Ball and socket joint
• B. Hinge joint
• C. Pivot joint
• D. Saddle joint

Answer: (B)

Flexion and extension reflect movement in a single plane, so the joint that best fits this primary action is the one designed to bend and straighten in one axis. A hinge joint is uniaxial and allows bending (flexion) and straightening (extension) in the sagittal plane, as seen at the elbow or knee. This single-plane motion defines its main function. Other joints enable broader or different movements: ball-and-socket joints offer rotation and movement in multiple directions; pivot joints allow rotation around an axis; saddle joints permit a mix of movements including some sideways motion. But for a joint whose main role is bending and straightening, the hinge joint is the best match.

Flexion and extension reflect movement in a single plane, so the joint that best fits this primary action is the one designed to bend and straighten in one axis. A hinge joint is uniaxial and allows bending (flexion) and straightening (extension) in the sagittal plane, as seen at the elbow or knee. This single-plane motion defines its main function. Other joints enable broader or different movements: ball-and-socket joints offer rotation and movement in multiple directions; pivot joints allow rotation around an axis; saddle joints permit a mix of movements including some sideways motion. But for a joint whose main role is bending and straightening, the hinge joint is the best match.