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The word radius is Latin for "ray". In the context of the radius bone, a ray can be thought of rotating around an axis line extending diagonally [clarification needed] from center of capitulum to the center of distal ulna. While the ulna is the major contributor to the elbow joint, the radius primarily contributes to the wrist joint. [5]
De Quervain syndrome causes pain over the styloid process of the radius. [3] [4] This is due to the passage of the inflamed extensor pollicis brevis tendon and abductor pollicis longus tendon around it. [4] [5] The styloid process of the radius is a useful landmark during arthroscopic resection of the scaphoid bone. [6]
However, the term describes the shape of a bone, not its size, which is relative. Long bones are found in the arms (humerus, ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges). Long bones function as levers; they move when muscles contract. [1]
The carpal bones function as a unit to provide a bony superstructure for the hand. [5]: 708 The scaphoid is also involved in movement of the wrist. [1]: 6 It, along with the lunate bone, articulates with the radius and ulna to form the major bones involved in movement of the wrist. [5]
The head of the radius has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum of the humerus. The circumference of the head is smooth; it is broad medially where it articulates with the radial notch of the ulna , narrow in the rest of its extent, which is embraced by the annular ligament .
The radial notch of the ulna (lesser sigmoid cavity) is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius. It is concave from before backward, and its prominent extremities serve for the attachment of the annular ligament.
The capitulum is a rounded eminence forming the lateral part of the distal humerus. The head of the radius articulates with the capitulum. Capitulum on the lateral side and trochlea on the medial side of the humerus. The trochlea is spool-shaped medial portion of the distal humerus and articulates with the ulna. Trochlea of the humerus
Radial aplasia is a congenital defect which affects the formation of the radius bone in the arm. The radius is the lateral bone (thumb side) which connects the humerus of the upper arm to the wrist via articulation with the carpal bones. A child born with this condition has either a short or absent radius bone in one or both of his or her arms.