A 16-year-old patient who is six months post wrist fracture is in for a follow up visit. The nurse assesses the range of motion (ROM) of the affected arm and notes which bones are involved in pronation and supination of the forearm?

A. Phalanges and clavicle: The phalanges are the distal bones of the digits involved in grasping, while the clavicle anchors the upper limb to the axial skeleton. Neither bone participates in the rotational mechanics of the forearm. Their anatomical positions are too distal and proximal, respectively, to influence radioulnar rotation. B. Metacarpal and carpal: These bones form the structural framework of the hand and the wrist joint proper. While they move as a unit during forearm rotation, they do not provide the pivot mechanism required for pronation or supination. Their primary movements include flexion, extension, and radial or ulnar deviation. C. Humerus and scapula: These bones constitute the glenohumeral joint, which allows for circumduction and rotation of the entire upper extremity. While the humerus provides the proximal origin for some forearm muscles, it does not rotate during isolated forearm supination. The scapula serves as a stable base for shoulder mobility. D. Radius and ulna: The proximal and distal radioulnar joints allow the radius to rotate around the relatively stationary ulna. This specialized articulation enables the palm to turn upward (supination) or downward (pronation). Functional integrity of these two bones is essential for common activities of daily living following a fracture.