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    Related Topics

    From Musculoskeletal System

    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.
    Carpals (8 bones)
    8 wrist bones.
    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Triceps Brachii
    Muscle responsible for elbow extension.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Biceps Tendon
    Tendon that attaches the biceps muscle to the bone.
    Sesamoid Bones
    e.g., patella, some found in hands/feet.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Temporalis
    Muscle involved in closing the jaw.
    Ball-and-Socket Joints
    e.g., shoulder, hip
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Symphyses
    Cartilaginous joints where bones are connected by fibrocartilage.
    Sacrum
    Triangular bone at the base of the spine.
    Deltoid
    Shoulder muscle responsible for arm abduction.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Annular Ligament
    The annular ligament is a strong fibrous band encircling the head of the radius, stabilizing the proximal radioulnar joint and allowing smooth rotation of the forearm.
    Sternum
    Breastbone located in the center of the chest.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Quadriceps Tendon
    Tendon that connects the quadriceps to the patella.
    Posterior Cruciate Ligament (PCL)
    Knee ligament that stabilizes the joint.
    Soleus
    Calf muscle responsible for plantarflexion of the foot.
    Occipital Bone
    Bone forming the back and base of the skull.
    Tibialis Anterior
    Muscle that dorsiflexes and inverts the foot.

    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? The metatarsals are the bones in the feet that connect to the toes.