Elbow hinge joint anatomy

Steps:

• Identify hinge joints as synovial joints allowing uniaxial movement like flexion-extension.
• Locate the forearm as containing radius and ulna bones, connecting to the humerus at the elbow.
• Recall the elbow's primary hinge component is the humeroulnar articulation.
• Confirm via anatomy: humerus trochlea fits ulna's trochlear notch for hinge action.

Why D is correct:

• The humeroulnar joint is defined as a hinge joint, where the humerus's trochlea articulates with the ulna's olecranon and trochlear notch for pure flexion-extension.

Why the others are wrong:

• A: Humerus and scapula form the glenohumeral ball-and-socket joint at the shoulder, allowing multiaxial rotation.
• B: Radius and ulna form pivot joints (proximal/distal radioulnar) for forearm pronation-supination, not hinging.
• C: Scapula articulates with humerus, not radius; no direct forearm hinge exists here.

Final answer: D