The upper limb bones form a complex structure, enabling a wide range of motion and dexterity. From the clavicle to the phalanges, each bone plays a crucial role in supporting and moving the arm and hand.

These bones connect through various joints, allowing for different types of movement. Understanding the anatomy and function of upper limb bones is essential for grasping how we perform everyday tasks and complex movements.

Bones of the Upper Limb

Bones of the upper limb (part of the appendicular skeleton)

• Clavicle
  • S-shaped bone articulates with manubrium of sternum medially and acromion of scapula laterally
  • Functions as strut to hold upper limb away from trunk
• Scapula
  • Triangular, flat bone located on posterior aspect of thorax
  • Key features include spine (prominent posterior ridge), acromion (lateral extension of spine articulating with clavicle), glenoid cavity (shallow socket articulating with head of humerus), and coracoid process (anterior projection serving as attachment point for muscles and ligaments)
• Humerus
  • Long bone of arm with rounded proximal head articulating with glenoid cavity of scapula
  • Greater and lesser tubercles serve as attachment points for rotator cuff muscles
  • Deltoid tuberosity is roughened lateral surface area for attachment of deltoid muscle
  • Medial and lateral epicondyles are distal projections serving as attachment points for forearm muscles
• Radius
  • Lateral bone of forearm with proximal head articulating with capitulum of humerus and radial notch of ulna
  • Radial tuberosity is roughened medial surface area for attachment of biceps brachii tendon
  • Distal styloid process serves as attachment point for brachioradialis muscle and ligaments
• Ulna
  • Medial bone of forearm with proximal olecranon forming point of elbow and serving as attachment point for triceps brachii muscle
  • Anterior coronoid process articulates with trochlea of humerus
  • Distal styloid process serves as attachment point for ulnar collateral ligament of wrist
• Carpals
  • Eight small bones arranged in proximal (scaphoid, lunate, triquetrum, pisiform) and distal (trapezium, trapezoid, capitate, hamate) rows forming wrist
• Metacarpals
  • Five bones forming palm of hand numbered I-V from lateral to medial
• Phalanges
  • Bones of fingers with each having three (proximal, middle, distal) except thumb which has two (proximal, distal)

Articulations of upper limb bones

• Sternoclavicular joint
  • Articulation between sternal end of clavicle and manubrium of sternum
  • Saddle-type synovial joint allowing limited multi-planar movement
• Acromioclavicular joint
  • Articulation between acromion of scapula and acromial end of clavicle
  • Plane-type synovial joint allowing limited gliding movements
• Glenohumeral (shoulder) joint
  • Articulation between glenoid cavity of scapula and head of humerus
  • Ball-and-socket synovial joint allowing wide range of multi-planar motion
• Elbow joint
  • Articulation between trochlea of humerus, trochlear notch of ulna, and head of radius consisting of humeroulnar (hinge-type allowing flexion/extension) and humeroradial (pivot-type allowing rotation during pronation/supination) joints
• Proximal radioulnar joint
  • Articulation between head of radius and radial notch of ulna
  • Pivot-type synovial joint allowing rotation of radius during pronation/supination
• Distal radioulnar joint
  • Articulation between head of ulna and ulnar notch of radius
  • Pivot-type synovial joint allowing rotation of radius during pronation/supination
• Wrist (radiocarpal) joint
  • Articulation between distal radius and proximal carpal row
  • Condyloid-type synovial joint allowing flexion, extension, abduction, adduction of hand
• Intercarpal joints
  • Articulations between adjacent carpal bones
  • Plane-type synovial joints allowing limited gliding movements
• Carpometacarpal joints
  • Articulations between distal carpal row and metacarpal bases
  • Plane-type synovial joints except thumb carpometacarpal joint which is saddle-type allowing wider range of motion
• Metacarpophalangeal joints
  • Articulations between metacarpal heads and proximal phalanx bases
  • Condyloid-type synovial joints allowing flexion, extension, abduction, adduction
• Interphalangeal joints
  • Articulations between adjacent phalanges
  • Hinge-type synovial joints allowing flexion and extension

Carpal tunnel anatomy and significance

• Carpal tunnel
  • Narrow passageway on palmar wrist aspect bordered by carpal bones (floor) and transverse carpal ligament (roof)
  • Contains median nerve and flexor tendons of fingers and thumb
• Functional significance
  • Allows passage of median nerve and flexor tendons from forearm to hand
  • Protects median nerve and flexor tendons from damage during wrist movements
• Clinical relevance: Carpal tunnel syndrome
  • Compression of median nerve within carpal tunnel
  • Causes include flexor tendon inflammation (repetitive strain) and conditions reducing carpal tunnel size (wrist fractures, arthritis, pregnancy)
  • Symptoms are pain, numbness, tingling in thumb, index, middle, lateral half of ring finger and thenar muscle weakness and atrophy in severe cases
  • Diagnosed by clinical exam (Tinel's sign, Phalen's test) and nerve conduction studies
  • Treated conservatively with wrist splinting, NSAIDs, corticosteroid injections or surgically by carpal tunnel release (transverse carpal ligament division to decompress median nerve)

Upper Limb Anatomy: Bone Landmarks and Structural Features

• Long bones (e.g., humerus, radius, ulna) have specific structural features:
  • Diaphysis: shaft of the bone
  • Epiphyses: proximal and distal ends of the bone
  • Metaphyses: regions between diaphysis and epiphyses
• Bone landmarks serve as important attachment points for muscles, ligaments, and tendons:
  • Processes: bony projections (e.g., coracoid process of scapula)
  • Tuberosities: roughened areas for muscle attachment (e.g., radial tuberosity)
  • Tubercles: small, rounded projections (e.g., greater and lesser tubercles of humerus)
• Synovial joints in the upper limb allow for various types of movement:
  • Lined with synovial membrane producing synovial fluid for lubrication
  • Surrounded by joint capsule for stability and protection