Functional Anatomy of the Elbow

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Introduction[edit | edit source]

Key Terms[edit | edit source]

Elbow Structure[edit | edit source]

Three bones makes up the elbow joint: the distal end of humerus and the proximal ends of ulna and radius. The ulna and the radius are both forearm bones which form the wrist joint at their distal end.

The distal end of humerus includes the medial and lateral columns, medial and lateral epicondyles, and two articular surfaces:

  • Medial and lateral columns
    • The distal end of the medial column includes the medial epicondyle with the insertion of forearm flexor muscles and the medial humeral trochlea
    • The distal end of the lateral column includes the capitellum and more proximally the lateral epicondyle with the insertion of the forearm extensor muscles
  • Medial and lateral epicondyles
    • A large medial epicondyle is a bony projection located at the distal end of the medial supracondylar ridge of the humerus
    • A smaller lateral epicondyles located at the at the distal end of the lateral supracondylar ridge of the humerus. It is curved forward, and provides attachment point for the radial collateral ligament, and serves as the origin of the supinator and some forearm extensor muscles.
  • Articular surfaces
    • Medially located trochlea articulates with the ulna
    • Laterally located capitellum articulates with radius

The proximal radius consists of the radial head, neck and tuberosity:

  • The radial head is cylindrical which articulates with the capitellum of the humerus. The head rotates within the annular ligament to produce supination and pronation of the forearm.
  • The neck and tuberosity support the head and provide points of attachments for supinator brevis and biceps brachii

The proximal ulna

  • Olecranon process articulates with with distal humerus via trochlea and olecranon fossa
  • The projection of the medial margin is called sublime tubercle, which serves as an insertion for the ulnar collateral ligament

Bones, Articulations and Kinematics of the Elbow[edit | edit source]

Mobility and stability of the elbow joint is necessary for daily functions, sports , and recreational activities. [1] Static stabilisers provide elbow stability via ulnohumeral articulation, the medial collateral ligament and the lateral ulnar collateral ligament. The joint capsule, the medial and lateral collateral ligaments provide 50% of elbow stability. The remaining stabilisation is associated with the bony structure of the joint and dynamic stabilisers including all muscles crossing the elbow joint and providing joint compressive forces.

Bones and Articulations[edit | edit source]

Bones Articulations Characteristics Key palpation points
Humerus

Ulna

Humeroulnar joint Made up of the trochlear groove on the humerus and the trochlear notch on the ulna. In the literature the joint is described as a modified hinge joint, with approximately 5 degrees of internal and external rotation occurring at the extremes of flexion and extension.[2]
Humerus

Radius

Humeroradial joint Made up of the capitulation of the humerus and the head of the radius. Due its dual action in joint flexion/extension and supination/pronation it is referred as a hinge/pivot joint.
Radius

Ulna

Proximal radioulnar joint Made up of the head of radius articulates and the radial notch of the ulna. It is supplied the muscles, bones, and joint capsule to provide static and dynamic stabilisation of the joint.

Elbow Kinematics[edit | edit source]

When assessing elbow flexion and extension, the variation between individuals must be considered. It includes individuals with joint hyperlaxity who may hyperextend by over 10 degrees or bodybuilders who may flex only up to 130 degrees due to their muscle bulk. According to Morrey et al.[3], activities of daily living including dressing and hygiene require 140 degrees of elbow flexion, while 15 degrees of flexion is needed to tie a shoe. In general, most of the activities of daily living can be completed with 30 to 130 degrees of available elbow flexion, 50 degrees of forearm pronation, and 50 degrees of forearm supination.[3]For daily tasks performances, these ranges are required in a dominant upper extremity as the dominant forearm is in pronation.[4] Reduction in elbow pronation range of motion can be compensated to by shoulder abduction in some tasks performance. However there is no effective compensation mechanism for loss of elbow supination.[5] [6]

Joint Type of joint Plane of movement Motion Kinematics Closed pack position Open pack position
Humeroulnar joint Hinge joint Saggital Flexion

Extension

Flexion:135 degrees

Extension:0 degrees

full extension and maximum forearm supination 70 degrees of flexion with 10 degrees of forearm supination
Humeroradial joint Pivot joint Saggital

Transverse

Flexion/Extension

Pronation/supination

Pronation:80 degrees

Supination: 85 degrees

90 degrees of elbow flexion and 5 degrees of supination extension and forearm supination
Proximal radioulnar joint Synovial

Note: it is functionally a pivot joint, allowing for rotation motion between the radius and the ulna (radius rotates on the ulna)

Transverse Pronation

Supination

5 degrees of forearm supination 70 degrees of flexion and 35 degrees of forearm supination

Elbow Passive Range of Motion Assessment[edit | edit source]

Elbow Bursae[edit | edit source]

  • The olecranon bursa
    • the main bursa of the elbow complex
    • located posteriorly between the skin and the olecranon process
    • in healthy elbow there is no communication between the bursa and the elbow joint
    • suseptible to injury from direct trauma to the elbow due to its superficial location
  • Intratendinous bursa
  • Subtendinous bursa: between the triceps tendon and olecranon
  • Bicipitoradial bursa: separates the biceps tendon from the radial tuberosity
  • Subcutaneous medial epicondylar bursa
  • Subcutaneous lateral epicondylar bursa

Elbow Joint Capsule[edit | edit source]

The capsule of the elbow is connected to the annular ligament.

  • The anterior capsule extends between the coronoid and radial fossae, the edge of the coronoid process, and the annular ligament.
  • The posterior capsule extends between the olecranon fossa, along the medial and lateral articular margins of the greater sigmoid notch, and becomes an extension of the annular ligament.
  • There are inconsistent findings regarding joint capsule contribution to the passive stabilisation of the elbow. [7]

Ligaments of the Elbow[edit | edit source]

Key ligaments Origin Insertion Action/role Key palpation points
Ulnar collateral ligament or medial collateral ligament

Anterior bundle: anterior, central and posterior bands

Posterior bundle

Transverse segment

Anteroinferior aspect of the medial epicondyle Proximal aspect of the ulna The anterior band of the anterior bundle is taut throughout the arc of motion and is a primary static stabilizer of the elbow. The posterior bundle is taut only in flexion as it attaches posterior to the sagittal axis of rotation. The transverse segment has the least contribution to elbow stability. [1]
Radial collateral ligament or lateral collateral ligament Lateral epicondyle The annular ligament Provides stabilisation for the radial head
Annular ligament The anterior margin of the lesser sigmoid notch The posterior margin of the lesser sigmoid notch Encircles 80% of the radial head

Maintains the relationship between the head of the radius and the humerus and ulna Reduces the friction against the radial head during pronation and supination

Quadrate ligament Radial notch of the ulna The medial surface of the neck of the radius Provides structural support to the capsule of the proximal radioulnar joint

Muscles of the Elbow[edit | edit source]

Muscles are dynamic stabilisers of the elbow joint through compressive load applied to the joint when muscles contract. They can be grouped into elbow extensors located posteriorly, elbow flexors at the front of the joint, supinators positioned laterally and pronators medially in relation to the joint axis.

The following sections will include muscles according to their role in moving the elbow. Other functions of these muscles not related to the elbow motion are not included (e.g. biceps brachii flexes the shoulder and helps to stabilise the head of the humerus in the glenoid cavity).

Elbow Flexors[edit | edit source]

Muscle Origin Insertion Innervation Action
Pronator teres Medial epicondyle of the humerus via the common flexor tendon

The coronoid process of the ulna

The lateral surface of the radial shaft Median nerve (C6-C7) Elbow flexion

Elbow pronation

Brachialis The shaft of the humerus The coronoid process and tuberosity of the ulna Musculocutaneous nerve (medial portion of the muscle)

Radial nerve (lateral portion of the muscle)

Pure elbow flexor
Brachioradialis The lateral supracondylar ridge The styloid process of the radius Radial nerve (C5-C6) Elbow flexor when the forearm is neutral Involved in supination and pronation depending on the position of the forearm
Biceps brachii:

Short head(SH) Long head(LH)

SH: the coracoid process of the scapula

LH: the supraglenoid tubercle of the scapula

SH/LH: radial tuberosity Musculocutaneous nerve Flexes the elbow joint, particularly when the forearm is supinated.

Assists with forearm supination

Elbow Extensors[edit | edit source]

Muscle Origin Insertion Innervation Action
Anconeus Lateral epicondyle The shaft and olecranon of the ulna Radial nerve (C6-C8) Assists in elbow extension
Triceps brachii

Long head (LH) Lateral head (LTH) Medial head (MH)

LH: infraglenoid tubercle of the scapula

LTH: lateral surface of the humeral shaft

MH: medial surface of the humeral shaft

LH/LTH/MH: olecranon of the ulna Radial nerve:

LH:C7

LTH:C6

MH:C8

Primary extensor of the elbow

Elbow Pronators[edit | edit source]

Muscle Origin Insertion Innervation Action
Pronator teres Medial epicondyle of the humerus via the common flexor tendon

The coronoid process of the ulna

The lateral surface of the radial shaft Median nerve (C6-C7) Elbow flexion

Elbow pronation

Pronator quadratus The oblique ridge of the ulnar shaft The anterior surface of the radial shaft. The anterior interosseous nerve Pulls the distal end of the radius over the ulna, which result

in the pronation of the radioulnar joint.

Brachioradialis The lateral supracondylar ridge The styloid process of the radius Radial nerve (C5-C6) Elbow flexor when the forearm is neutral

Involved in pronation to neutral when the forearm is in supination

Elbow Supinators[edit | edit source]

Muscle Origin Insertion Innervation Action
Supinator Supinator crest of the ulna

The radial collateral ligament The annular ligament The lateral epicondyle of the humerus

Lateral surface of the radial shaft Radial nerve (C5-C6) Prime supinator of the forearm
Brachioradialis The lateral supracondylar ridge The styloid process of the radius Radial nerve (C5-C6) Elbow flexor when the forearm is neutral

Assist in supinating the forearm to neutral when the forearm is in pronation

Biceps brachii:

Short head(SH) Long head(LH)

SH: the coracoid process of the scapula

LH: the supraglenoid tubercle of the scapula

SH/LH: radial tuberosity Musculocutaneous nerve Flexes the elbow joint, particularly when the forearm is supinated.

Assists with forearm supination

Innervation of the Elbow[edit | edit source]

The nerve supply to the elbow stems from the brachial plexus that originated in the shoulder. The brachial plexus is a network of nerves formed from the ventral rami of nerve roots C5 to T1. From proximal to distal, the brachial plexus is organised by roots, trunks, divisions, and cords.[8]

  • Musculocutaneous nerve: the terminal branch of the lateral cord of the brachial plexus
  • Median nerve: emerges from the lateral and medial cords of the brachial plexus
  • Radial nerve: arises from the posterior cord of the brachial plexus
  • Ulnar nerve: Continues from the medial cord of the brachial plexus within the axilla region. It does not innervate any muscles that move the elbow. [9]
Nerve Origin Brunches Motor fibres Sensory fibres
Median nerve Terminal branch of the medial cord of the brachial plexus (nerve roots C6-T1, can contain fibres from C5 in some individuals) Anterior interosseous nerve

Palmar cutaneous branch Motor branch in the hand

Flexor (anterior) compartment of the forearm: pronator teres and pronator quadratus muscles

Thenar and intrinsic hand muscles

Skin over thenar eminence, palmar aspect of the thumb, index, middle finger and radial half of the ring finger
Musculocutaneous nerve Terminal branch of the lateral cord of the brachial plexus (nerve roots C5-C7) Motor branches

Articular branches Lateral cutaneous nerve of the forearm

Flexor (anterior) compartment of the forearm: the coracobrachialis, biceps brachii, and brachialis muscles Cutaneous innervation of the lateral forearm
Radial nerve Posterior cord of brachial plexus (C5-T1) Posterior brachial cutaneous nerve, inferior lateral brachial cutaneous nerve, posterior antebrachial cutaneous nerve, muscular branches, deep branch of radial nerve, superficial branch of radial nerve Triceps brachii

Anconeus Brachioradialis

Central and posterior aspect of the forearm
Anterior interosseous nerve Median nerve Terminal branches around the wrist joint. Pronator quadratus Mainly a motor nerve. May supply some distal sensory branches

Vascular Supply of the Elbow[edit | edit source]

The elbow is supplied by the branches from the brachial artery. It is located near the skin surface. The brachial artery is used to measure the blood pressure and can be easily damaged during arm fractures.

Artery Origin Branches Supply
Deep brachial artery (profunda brachii artery) Brachial artery Nutrient arteries of humerus, deltoid branch, middle collateral artery, radial collateral artery Tricepc brachii, anconeus, brachialis, brachioradialis muscles; Lateral intermuscular septum; Radial nerve.
Superior ulnar collateral artery Anterior and posterior ulnar recurrent arteries

Periarticular arterial anastomosis of the elbow

Triceps brachii

Elbow joint

Inferior ulnar collateral artery Anterior ulnar recurrent artery (anastamoses)

Branch to superior ulnar collateral artery

Biceps and brachialis muscles
Ulnar artery Anterior and posterior ulnar recurrent arteries

Common interosseous artery, palmar carpal arch, superficial palmar arch, and dorsal carpal branch

The elbow joint, medial and central forearm muscles, median and ulnar nerves, and common flexor sheath
Radial recurrent artery The muscular branches The elbow joint, brachialis, brachioradialis, and other forearm muscles.

Clinical Relevance[edit | edit source]

  1. Medial epicondylopathy (golfer's elbow) presents with medial elbow and proximal forearm pain with activities requiring wrist flexion and forearm pronation. Clinical examination reveals tenderness from the medial epicondyle to the pronator teres and flexor carpi radial muscles. Degenerative changes at the origin of the flexor tendons due to micro trauma and overload can lead to development of this condition.[10]
  2. Pain located on the lateral side of the elbow can be the symptom consistent with the lateral tendinopathy, or the tennis elbow.[11]
  3. Popeye's deformity is "a pronounced bulging muscle in the distal aspect of the biceps region of the arm."[12]

Resources[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 Islam SU, Glover A, MacFarlane RJ, Nisarg Mehta N, Waseem M. The Anatomy and Biomechanics of the Elbow. The Open Ortopaedic Journal 2020;14:95-99
  2. Stroyan M, Wilk KE. The Functional Anatomy of the Elbow Complex. JOSPT 1995; 17(6): 279-288.
  3. 3.0 3.1 Morrey BF, Askew LJ, Chao EY. A biomechanical study of normal functional elbow motion. J Bone Joint Surg Am. 1981 Jul;63(6):872-7.
  4. Haverstock JP, King GJW, Athwal GS, Johnson JA, Langohr GDG. Elbow motion patterns during daily activity. J Shoulder Elbow Surg. 2020 Oct;29(10):2007-2014.
  5. Bryce CD, Armstrong AD. Anatomy and biomechanics of the elbow. Orthop Clin North Am. 2008 Apr;39(2):141-54, v.
  6. Soubeyrand M, Assabah B, Bégin M, Laemmel E, Dos Santos A, Crézé M. Pronation and supination of the hand: Anatomy and biomechanics. Hand Surg Rehabil. 2017 Feb;36(1):2-11.
  7. Nielsen KK, Olsen BS. No stabilizing effect of the elbow joint capsule. A kinematic study. Acta Orthop Scand. 1999 Feb;70(1):6-8.
  8. Xuan D. Exploring Shoulder Anatomy. Plus 2023
  9. Xuan D. Exploring Elbow Anatomy. Plus 2023
  10. Ott N, Van Riet R, Hackl M, Wegmann K, Müller LP, Leschinger T. Medial epicondylopathy—microtrauma and pathologic overuse as a cause of degeneration of the flexor tendons. Obere Extremität 2020;15: 289–294
  11. Bateman M, Evans JP, Vuvan V, Jones V, Watts AC, Phadnis J, Bisset LM, Vicenzino B, COS-LET Authorship Group. Development of a core outcome set for lateral elbow tendinopathy (COS-LET) using best available evidence and an international consensus process. British Journal of Sports Medicine 2022;56:657-666.
  12. Roberts D, Bell D, Popeye sign. Reference article, Radiopaedia.org. Available from https://doi.org/10.53347/rID-76988 [last access 7.08.2023]