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    Related Topics

    From Musculoskeletal System

    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Acromioclavicular Joint
    The acromioclavicular joint connects the clavicle and scapula at the top of the shoulder, enabling smooth scapular motion and stability during arm movements.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Vertebral Column
    Spinal column consisting of vertebrae.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    Ethmoid Bone
    Bone forming part of the nasal cavity and the orbit.
    Skull
    Bony structure of the head that encases the brain.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Mandible
    Lower jawbone that houses the teeth.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Symphyses
    Cartilaginous joints where bones are connected by fibrocartilage.
    Masseter
    Muscle that elevates the mandible.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Medial Collateral Ligament (MCL)
    Knee ligament that stabilizes the inner knee.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Sternum
    Breastbone located in the center of the chest.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Facial Bones
    Bones forming the structure of the face.
    Rotator Cuff Muscles
    Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.
    Carpals (8 bones)
    8 wrist bones.
    Coccygeus
    Pelvic floor muscle supporting the coccyx.
    Flexor Tendons
    Tendons that help flex the fingers and toes.

    Radius

    Reviewed by our medical team

    Forearm bone on the thumb side.

    1. Overview

    The radius is one of the two long bones of the forearm, the other being the ulna. Located on the lateral (thumb) side of the forearm, the radius plays a critical role in forearm rotation and wrist articulation. It is essential for pronation and supination, allowing the hand to rotate palm-up or palm-down. The radius also contributes to load-bearing and mobility of the upper limb.

    2. Location

    The radius is positioned laterally in the forearm, parallel to the ulna:

    • Proximally: Articulates with the capitulum of the humerus and the radial notch of the ulna at the elbow joint.

    • Distally: Articulates with the carpal bones (scaphoid and lunate) and the ulnar head at the wrist joint.

    • Lateral to: The ulna in anatomical position (thumb side).

    3. Structure

    The radius is a long bone with three key regions:

    • Proximal end:

      • Head: Disc-shaped; articulates with the humerus and ulna.

      • Neck: Narrow region below the head.

      • Radial tuberosity: A rough prominence below the neck; insertion site for the biceps brachii tendon.

    • Shaft (body):

      • Triangular in cross-section with anterior, posterior, and lateral surfaces.

      • Interosseous border on the medial aspect provides attachment for the interosseous membrane, connecting to the ulna.

    • Distal end:

      • Broad and flat.

      • Styloid process: Projects laterally and can be palpated near the wrist.

      • Ulnar notch: Articulates with the ulna.

      • Carpal articular surface: Articulates with the scaphoid and lunate bones of the wrist.

    4. Function

    The radius serves several critical functions in the upper limb:

    • Forearm rotation: Rotates over the ulna during pronation and supination, enabling turning of the palm.

    • Elbow joint motion: Participates in flexion and extension by articulating with the humerus.

    • Wrist articulation: Transmits forces between the hand and forearm; forms the major connection between forearm and carpal bones.

    • Muscle attachment: Provides insertion points for muscles such as biceps brachii, supinator, pronator teres, and others.

    5. Physiological role(s)

    While passive structurally, the radius contributes to various physiological and functional roles:

    • Force transmission: Bears and transmits load from the hand to the elbow, especially during weight-bearing or impact activities.

    • Fine motor control: Enables wrist mobility necessary for gripping, writing, and tool manipulation.

    • Proprioception: Contains sensory receptors that provide feedback about limb position and movement.

    • Joint alignment: Helps maintain congruent positioning of the wrist and elbow joints through ligament and muscle interactions.

    6. Clinical Significance

    The radius is involved in many orthopedic and sports-related injuries:

    • Colles’ fracture:

      • Fracture of the distal radius with dorsal displacement; common in falls on an outstretched hand (FOOSH), especially in the elderly.

    • Smith’s fracture:

      • Fracture of the distal radius with volar (palmar) displacement; typically from a fall onto a flexed wrist.

    • Galeazzi fracture-dislocation:

      • Fracture of the distal third of the radius with dislocation of the distal radioulnar joint.

    • Radial head fractures:

      • Common in elbow trauma; may limit pronation and supination and require surgical fixation depending on severity.

    • Osteomyelitis or tumors:

      • Infectious or neoplastic conditions may affect the radius, though less common than trauma-related issues.

    • Growth plate injuries:

      • In children, distal radial growth plate (physis) injuries must be monitored to prevent future deformity.

    Did you know? Your bones make up only 15% of your body weight.