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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]
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 .
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]
The humerus (/ ˈ h juː m ər ə s /; pl.: humeri) is a long bone in the arm that runs from the shoulder to the elbow.It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections.
Beneath the neck of the radius, on the medial side, is an eminence, the radial tuberosity; its surface is divided into: . a posterior, rough portion, for the insertion of the tendon of the biceps brachii.
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 major exception is when the joint between these bones, the distal radioulnar joint (or DRUJ), is unstable. When the DRUJ is unstable, the ulnar styloid may require independent treatment. An excessively long styloid process of the ulna can cause painful contact with the triquetral bone in the wrist, known as ulnar styloid impaction syndrome. [1]