Elbow joint anatomy and hinge movement

Steps:

• Identify the elbow joint as the articulation between the distal humerus and proximal ulna/radius.
• Recall that the primary elbow joint (humeroulnar) is a hinge joint enabling flexion and extension.
• Note that hinge joints permit movement in a single plane (sagittal).
• Eliminate options with incorrect bones or movement types.

Why B is correct:

• The humeroulnar joint forms the main elbow hinge between the ulna and humerus, allowing uniaxial movement (flexion/extension) in one plane, as defined by synovial joint classification.

Why the others are wrong:

• A: Scapula articulates at the shoulder, not the elbow.
• C: Ulna and radius form the radioulnar joint for rotation (pivot), not strictly in one plane.
• D: Humeroulnar movement is uniaxial (one plane), not triplanar like a ball-and-socket joint.

Final answer: B