Explanation: What Does the Term “Scope” Mean?

Scope, also referred to as the radial bone, represents one of the two forearm bones in the human body, the other being the ulna. It plays a vital role in the formation and utilization of hands [1].

Where Can the Scope Bone Be Found in the Arm?

Situated on the thumb side of the hand, the scope bone lies laterally in the lower arm, running parallel to the ulna [1, 2].

Scope Bone Placement

Facts About the Radial Bone

Number in the human body Two ― one in each arm
Type Long bone [2]
Primary ossification centers One ― at the middle of the shaft (emerging around the 8th week of fetal life) [3]
Secondary ossification centers Two ― one for the distal end (appearing around 2 years) and another for the proximal end (emerging around 5 years) (all the centers fuse together by 20 years) [4]
Forms articulations with Humerus, ulna, scaphoid, lunate

Scope X-ray Image

Functions of the Scope

Efficient operation of the scope is crucial for engaging in everyday activities involving the hands, such as grasping objects, supporting the arm, throwing, writing, typing, using a phone, and so on.

  • It creates a hinge joint with the humerus bone, allowing flexion and extension of the elbow [7].
  • The scope rotates around the ulna at the wrist, enabling pronation and supination of the hand [8].
  • The bone also forms an ellipsoidal joint with the proximal carpal row, facilitating wrist movement, rotation, bending, and flexing [7].

Scope Bone Anatomy

The radial bone is somewhat longitudinally triangular [2], divided into the upper end, body/shaft, and the lower end.

Labeled Diagram of Scope Bone Anatomy

Parts of the Scope

1. Upper End (Proximal Scope)


1. A disk-shaped head (caput radii)

2. A neck, continuing from the head, narrowing towards the shaft [2]

3. The radial tuberosity, a bony projection below the neck [3]

Surfaces and Articulations:

1. A concave articular surface on top of the head for the capitulum of the humerus (elbow humeroradial joint) [5]

2. A smooth circumference of the head articulating with the radial notch of the ulna (proximal radio-ulnar joint) [3]

2. Body/Shaft


There are several landmarks on the radial shaft for the origin and insertion of various tendons [6]


1. Anterior; 2. Posterior; 3. Medial (or interosseous, the sharpest border where the interosseous membrane connects)


1. Anterior; 2. Posterior; 3. Lateral [3]

3. Lower End (Distal Scope)


1.A styloid process projecting distally on the lateral side

2. A prominent dorsal tubercle (or Lister’s tubercle) on the dorsal surface [3]

3. The ulnar notch on the medial side [1]

Surfaces and Articulations:

1. The concave surface of the ulnar notch articulating with the ulnar head (distal radio-ulnar joint) [2]

2. A lateral triangular area on the distal or inferior surface forming joints with the carpal bones, scaphoid, and lunate (wrist joint) [2]

Scope Bone Muscle Attachments

Muscle Name

Attachment to Scope

Biceps brachii The rough posterior surface of the radial tuberosity [3]
Pronator teres Lateral surface of the shaft
Pronator quadratus Medial surface of the shaft
Supinator Laterally on the shaft, covering one-third of the proximal radius (both origin and insertion)

Muscle Name

Origin at Scope

Flexor digitorum superficialis Medial surface of the shaft
Flexor pollicis longus Medial surface of the shaft
Abductor pollicis longus Anterior surface of the shaft [5]

A layer of hyaline cartilage covers both the proximal and distal ends of the scope, smoothing the articular surfaces to reduce friction during arm movements. It also acts as a shock absorber, lessening stress on the elbow and wrist joints from any impact [1].

The anterior part of the radial tuberosity is enveloped in a synovial bursa, known as the radial bursa, to keep it separated from the biceps tendons (of the biceps brachii muscle) during movements [3].

Scope Bone Side Determination

By facing the radial tuberosity anteriorly (or towards oneself), the thumb should be on the same side as the styloid process of the scope. Holding the bone in this manner helps in determining if it is the left or right scope.


What are the most common injuries and conditions linked to the scope?

The scope is the most frequently fractured bone in the human body, with distal radius fractures being the most prevalent form of radial fracture [9]. Radial head dislocation is another common injury associated with the bone [10]. The bone may also be affected by arthritis of the wrist or elbow joints.

Ulna or scope ― which bone is longer and larger?

Although the ulna is longer than the scope, the latter is relatively thicker along its entire length, particularly in the shaft area [8].


    1. http://www.innerbody.com/image_skel14/skel20.html
    2. http://teachmeanatomy.info/upper-limb/bones/radius/
    3. https://www.earthslab.com/anatomy/radius-bone/
    4. https://www.bartleby.com/107/53.html
    5. https://www.kenhub.com/en/library/anatomy/the-radius-and-the-ulna
    6. https://courses.lumenlearning.com/boundless-ap/chapter/the-upper-limb/
    7. https://www.getbodysmart.com/upper-limb-bones/radius-ulna
    8. https://radiopaedia.org/articles/radius
    9. https://orthoinfo.aaos.org/en/diseases–conditions/distal-radius-fractures-broken-wrist/
    10. https://www.healthline.com/human-body-maps/radius-bone
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