Functional Anatomy of the Elbow
Original Editor - Ewa Jaraczewska
Top Contributors - Ewa Jaraczewska, Jess Bell and Kim Jackson
Introduction[edit | edit source]
The elbow is an "intricate mechanical system."[1] It comprises the humerus and two forearm bones: radius and ulna. The relationship between the joint articulation and the soft tissue makes the elbow one of the most stable joints. [2] Performing daily activities relies heavily on this joint stability.[3] Hence, the elbow instability as a result of the damage to the bone joint surface and the ligament structure can cause pain and severe impairment in daily and athletic performances.
This article discusses the key anatomical structures of the elbow complex, including the bony structures, articulations, ligaments, muscles, nerves and the vascular supply.
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. [2] 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.[4] | |
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.[5], 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.[5]For daily tasks performances, these ranges are required in a dominant upper extremity as the dominant forearm is in pronation.[6] 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.[7] [8]
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. [9]
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. [2] | |
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.[10]
- 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. [11]
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]
- 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.[12]
- Pain located on the lateral side of the elbow can be the symptom consistent with the lateral tendinopathy, or the tennis elbow.[13]
- Popeye's deformity is "a pronounced bulging muscle in the distal aspect of the biceps region of the arm."[14]
Resources[edit | edit source]
- Li K, Zhang J, Liu X, Zhang M. Estimation of continuous elbow joint movement based on human physiological structure. Biomed Eng Online. 2019 Mar 20;18(1):31.
- Special Tests for the Elbow Exam https://www.sportsmedreview.com/blog/special-tests-elbow-exam/
- Gates DH, Walters LS, Cowley J, Wilken JM, Resnik L. Range of Motion Requirements for Upper-Limb Activities of Daily Living. Am J Occup Ther. 2016 Jan-Feb;70(1):7001350010p1-7001350010p10.
References[edit | edit source]
- ↑ Li K, Zhang J, Liu X, Zhang M. Estimation of continuous elbow joint movement based on human physiological structure.Biomed Eng Online. 2019 Mar 20;18(1):31.
- ↑ 2.0 2.1 2.2 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
- ↑ Xu G, Chen W, Yang Z, Yang J, Liang Z, Li W. Finite Element Analysis of Elbow Joint Stability by Different Flexion Angles of the Annular Ligament. Orthop Surg. 2022 Nov;14(11):2837-2844.
- ↑ Stroyan M, Wilk KE. The Functional Anatomy of the Elbow Complex. JOSPT 1995; 17(6): 279-288.
- ↑ 5.0 5.1 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.
- ↑ 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.
- ↑ Bryce CD, Armstrong AD. Anatomy and biomechanics of the elbow. Orthop Clin North Am. 2008 Apr;39(2):141-54, v.
- ↑ 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.
- ↑ Nielsen KK, Olsen BS. No stabilizing effect of the elbow joint capsule. A kinematic study. Acta Orthop Scand. 1999 Feb;70(1):6-8.
- ↑ Xuan D. Exploring Shoulder Anatomy. Plus 2023
- ↑ Xuan D. Exploring Elbow Anatomy. Plus 2023
- ↑ 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
- ↑ 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.
- ↑ Roberts D, Bell D, Popeye sign. Reference article, Radiopaedia.org. Available from https://doi.org/10.53347/rID-76988 [last access 7.08.2023]