Joints of Upper Limb

Pectoral Girdle Joints - Shoulder's Anchor

• Sternoclavicular (SC) Joint:
  • Type: Saddle synovial; only true bony articulation of upper limb to axial skeleton.
  • Components: Medial clavicle, manubrium, 1st costal cartilage. Intra-articular disc present.
  • Stability: Strong capsule; Ant/Post Sternoclavicular, Interclavicular, Costoclavicular (primary stabilizer) ligaments.
  • Movements: Elevation/depression, protraction/retraction, rotation (~30-35°).
• Acromioclavicular (AC) Joint:
  • Type: Plane synovial.
  • Components: Lateral clavicle, acromion. Incomplete intra-articular disc.
  • Stability: Weak capsule; Acromioclavicular ligament. Coracoclavicular ligament (conoid & trapezoid) is main extrinsic stabilizer, preventing superior displacement of clavicle.
  • Movements: Gliding, allows scapular rotation on thoracic cage (scapulothoracic rhythm).

⭐ The SC joint is rarely dislocated due to its strong ligamentous support; posterior dislocation is a medical emergency due to risk to mediastinal structures.

Glenohumeral Joint - Mobile Marvel

• Type: Synovial, ball-and-socket, multiaxial.
• Articular Surfaces: Large, round humeral head & shallow glenoid fossa of scapula.
  • Glenoid labrum: fibrocartilaginous rim; deepens fossa by 50%.
• Capsule: Lax inferiorly (allows abduction); attaches to anatomical neck of humerus & glenoid margin.
  • Openings: long head of biceps tendon, subscapular bursa.
• Ligaments:
  • Glenohumeral (superior, middle, inferior): thickenings of anterior capsule.
  • Coracohumeral: superiorly strengthens capsule.
  • Transverse humeral: holds biceps tendon in intertubercular groove.
• Stability: Primarily dynamic (muscles) > static (ligaments).
  • Rotator cuff muscles (SITS): Supraspinatus, Infraspinatus, Teres minor, Subscapularis.
  • Long head of biceps brachii.
• Movements: Flexion, extension, abduction, adduction, medial rotation, lateral rotation, circumduction.

• Blood Supply: Anterior & posterior circumflex humeral arteries, suprascapular artery.
• Nerve Supply: Suprascapular, axillary, lateral pectoral nerves (Hilton's Law).

⭐ Most commonly dislocated large joint in the body; usually anteriorly (anteroinferiorly). Axillary nerve is most commonly injured in anterior dislocation.

📌 SITS for Rotator Cuff muscles: Supraspinatus, Infraspinatus, Teres minor, Subscapularis.

Elbow & Radioulnar Joints - Flexion & Rotation Hub

• Elbow Joint (Synovial Hinge): A complex joint.
  • Components:
    • Humeroulnar: Trochlea (humerus) with Trochlear notch (ulna). Primary for flexion/extension.
    • Humeroradial: Capitulum (humerus) with Head (radius).
  • Movements: Flexion (Brachialis, Biceps brachii, Brachioradialis), Extension (Triceps brachii, Anconeus).
  • Ligaments: Medial (Ulnar) Collateral Lig. (MCL/UCL), Lateral (Radial) Collateral Lig. (LCL/RCL).
  • Carrying Angle: ~5-15° valgus; more pronounced in females.
• Radioulnar Joints (Synovial Pivot):
  • Superior: Head of radius in radial notch of ulna; stabilized by Annular ligament.
  • Inferior: Head of ulna in ulnar notch of radius; Triangular Fibrocartilage Complex (TFCC) is key.
  • Movements: Pronation (Pronator teres, Pronator quadratus), Supination (Supinator, Biceps brachii).

  ⭐ Nursemaid's elbow (pulled elbow): Subluxation of radial head under annular ligament in children (typically 1-4 years) due to sudden pull on extended, pronated forearm.

Wrist & Hand Joints - Dexterity's Domain

• Radiocarpal (Wrist): Ellipsoid. Radius & disc with Scaphoid, Lunate, Triquetrum. Ulna excluded. Actions: Flex/Ext, Add/Abd, Circumduction.
• Intercarpal: Plane. Gliding between carpals. Midcarpal joint important.
• **Carpometacarpal (CMC):
  • 1st (Thumb): Saddle. Trapezium & 1st Metacarpal. Key for opposition.
  • 2nd-5th: Plane. Limited movement.
• Metacarpophalangeal (MCP): Condyloid. Actions: Flex/Ext, Add/Abd.
• Interphalangeal (IP): Hinge. PIP & DIP in fingers. Actions: Flex/Ext only.

⭐ The 1st CMC joint (thumb), a saddle type, is vital for opposition.

High‑Yield Points - ⚡ Biggest Takeaways

• Shoulder joint: Most mobile, commonest anterior dislocation; rotator cuff for stability.
• Elbow joint: Hinge & pivot functions; site of Nursemaid's elbow and carrying angle.
• Wrist joint: Condyloid type; scaphoid fracture risks avascular necrosis.
• Sternoclavicular joint: Saddle type; sole bony link to axial skeleton.
• Acromioclavicular joint: Plane type; common for separation.
• Axillary nerve vulnerable in shoulder dislocation; Median nerve in carpal tunnel.
• Pronation/supination occurs at radioulnar joints (pivot).