Introduction

The elbow joint, although non–weight-bearing, is among the most complex articulations in the human body (see Image. Ligamentous Anatomy of the Left Elbow, Anterior View). The primary articulation in this synovial hinge joint is between the distal humerus and proximal ulna, supplemented by connections between the proximal radius and humerus and between the proximal radius and ulna. The resulting 3 components—the ulnohumeral, radiohumeral, and proximal radioulnar joints—function together to permit flexion, extension, pronation, and supination. Numerous muscles from both the arm and forearm cross or attach to at least 1 element of the elbow complex, contributing to the high frequency of injuries observed in athletic activities. After the shoulder, the elbow is the 2nd most commonly injured joint in sports-related trauma.[1]

A broad spectrum of conditions affects the elbow, including medial collateral ligament (MCL) tears, medial epicondylitis, distal biceps tendon ruptures, osteochondritis dissecans, olecranon bursitis, and pediatric radial head subluxation. The elbow also holds substantial surgical significance, with procedures such as ligament reconstruction, tendon reinsertion, arthroscopic debridement, osteochondral fixation, and bursectomy frequently employed to restore function or address persistent pathology. A deeper understanding of elbow anatomy, joint mechanics, and functional biomechanics allows clinicians to recognize injury patterns accurately, optimize diagnostic evaluation, and select appropriate therapeutic interventions.

Structure and Function

The elbow is a complex synovial joint that permits substantial motion and functional capacity, primarily through flexion and extension, while also enabling forearm-derived hand motion in the form of supination and pronation. Stability is provided chiefly by the osseous articulation between the humeral trochlea and the ulnar olecranon (see Image. Elbow Joint Structures). The olecranon forms a wrench-like configuration in which the trochlear notch surrounds the humeral trochlea and serves as the primary pivot during flexion and extension. The near 180° curvature of the trochlear notch and the broad, grooved contour of the trochlea create a tightly conforming interface that enhances joint stability.

Beyond the ulnohumeral articulation, major stabilizing support derives from the MCL and the lateral collateral ligament (LCL). Both of these fibrous bands integrate into the joint capsule to reinforce structural integrity (see Image. Ligamentous Structures of the Elbow).

The MCL, also known as the ulnar collateral ligament (UCL), is a triangular ligament consisting of 3 bands: the anterior oblique, posterior oblique, and transverse (Cooper) ligaments (see Image. Ulnar Collateral Ligament and Ulnar Nerve).[2] The anterior oblique ligament originates from the anterior-inferior surface of the medial epicondyle of the humerus and attaches to the coronoid process of the ulna. This fibrous structure constitutes the strongest medial stabilizer of the elbow and resists excessive valgus stress. The posterior oblique ligament also arises from the medial epicondyle and courses posteriorly to attach to the olecranon. The transverse ligament spans between the coronoid process and the tip of the olecranon, forming a bridge between the anterior and posterior bands.

The LCL consists of 3 components: the annular, lateral radial collateral, and lateral ulnar collateral ligaments. Collectively, these structures provide stability against varus stress and maintain posterolateral rotational stability. The lateral ulnar collateral ligament is the principal stabilizer of posterolateral rotation, originating from the lateral humeral epicondyle and inserting on the supinator crest of the ulna, crossing the inferior aspect of the radial head. The annular ligament encircles the neck of the radius, originating and inserting at the sigmoid notch of the ulna, and stabilizes the proximal radioulnar joint.

The cubital tunnel is a clinically significant passage for the ulnar nerve. The arcuate ligament forms the roof of this area, also known as the Osborne ligament, which connects the medial epicondyle to the olecranon, while the floor consists of the MCL (see Image. Osborne Ligament in the Cubital Tunnel). The anterior, posterior, and lateral borders are defined by the medial epicondyle, the medial head of the triceps brachii, and the olecranon, respectively. The ulnar nerve’s superficial position at the cubital tunnel, especially where the Osborne ligament forms the tunnel roof, explains why striking this area causes the characteristic electric shock or "funny bone" sensation radiating down the forearm toward the ring and little fingers.[3]

The elbow joint contains a synovial membrane enclosed within a joint capsule, separated by fat pads located superficial to stress-prone regions, including the olecranon, coronoid, and radial fossae. Attachments to the brachialis and triceps brachii mobilize these pads during flexion and extension, creating space for bony processes. The olecranon bursa facilitates triceps function by providing lubrication between the olecranon and the triceps tendon.[4]

Embryology

Ossification of the bones comprising the elbow joint begins during the 12th week of gestation. The process starts in the distal epiphysis of the humerus, followed by the trochlear notch of the ulna and the radial head. By the end of the embryonic period, the groove between the olecranon process and the posterior aspect of the medial epicondyle becomes apparent. The ulnar nerve tunnel forms posterior to the medial epicondyle, followed by the development of the elbow joint cavity at the humeroulnar and humeroradial articulations. Subsequently, the annular ligament develops, and the joint cavity of the superior radioulnar joint is established.[5][6]

Blood Supply and Lymphatics

The elbow joint serves as a conduit for the majority of neurovascular structures in the upper extremity. The superficial course of many of these structures permits visualization using ultrasound. The brachial artery, a distal extension of the axillary artery, provides the principal arterial supply to the elbow. The branches of this blood vessel include the deep brachial artery, which courses posteriorly and gives rise to smaller vessels that anastomose with the radial artery. The brachial artery continues distally before dividing into the radial and ulnar arteries (see Image. Elbow Joint Arterial Anastomosis).

Major lymphatic structures surrounding the elbow include the deep and superficial cubital lymph nodes, as well as the epitrochlear and supratrochlear nodes, the latter comprising up to 5 nodes situated superior to the medial epicondyle. Lymphatic drainage progresses proximally through the deep brachial lymph nodes and ultimately empties into the axillary lymph nodes.[7]

Nerves

The nerves crossing the elbow joint predominantly innervate structures of the forearm and hand (see Image. Nerves and Blood Vessels of the Arm and Forearm, Anterior View). While not crossing the joint itself, the musculocutaneous nerve supplies the biceps brachii, which contributes to supination and some flexion, and the brachialis, the primary flexor of the elbow.

The radial nerve originates medially at the proximal humerus, spirals posteriorly and laterally through the spiral groove, and crosses the elbow as it enters the distal humeral radial groove. This nerve provides motor input to 5 muscles influencing the elbow—the lateral portion of the brachialis, anconeus, supinator, brachioradialis, and triceps brachii.

The ulnar nerve travels along the medial arm, running from the anterior to the posterior compartment, where it enters the cubital tunnel and ulnar nerve groove. This nerve supplies the muscles of the forearm and hand. The median nerve traverses the anterior aspect of the elbow and continues distally to innervate the forearm and hand muscles.

The lateral and medial antebrachial cutaneous nerves provide sensory innervation of the forearm. These nerves are derived from the musculocutaneous and radial nerves, respectively.[8]

Muscles

Numerous muscles cross and attach around the elbow joint, providing secondary stabilization. Most muscles originating near the elbow contribute minimally to joint motion, instead functioning as flexors and extensors of the wrist, hand, and digits. Elbow stability is reinforced through resistance to varus and valgus forces. Muscles generating varus force to counteract valgus stress include the flexor digitorum superficialis, flexor carpi ulnaris, flexor carpi radialis, and pronator teres. Muscles producing valgus force to resist varus stress include the extensor digitorum communis, extensor carpi radialis longus and brevis, anconeus, and extensor carpi ulnaris.

Primary elbow movers include flexors such as the biceps brachii, brachialis, and brachioradialis. The biceps brachii exerts a modest contribution to flexion and serves as the principal supinator. This muscle is unique in having 2 distal attachments: a laterally oriented tendon inserting on the proximal radius and a medially oriented aponeurosis extending into the proximal forearm fascia. Elbow extension is performed primarily by the triceps brachii, with minor contribution from the anconeus.[9]

Physiologic Variants

Several osseous and nonosseous variants exist within the elbow joint, some of which may impair function. Anatomical variability in this region can influence joint mechanics, neurovascular relationships, and susceptibility to pathology. Recognizing these atypical features is critical for surgical planning and the prevention of iatrogenic injury.

Pseudodefect of the capitellum represents a normal osseous variant characterized by a groove between the capitellum and lateral epicondyle. This groove is visible on magnetic resonance imaging and may be misinterpreted as an osteochondral defect.

The supracondylar process, a bony spur present in up to 3% of individuals, may be mistaken for a humeral osteochondroma. In cases of prominent supracondylar processes, compression of the median nerve and, rarely, the brachial artery, can occur due to a fibrous band known as the ligament of Struthers, which extends from the supracondylar process to the medial epicondyle.[10]

Ligamentous variations have also been documented. Multiple studies have identified 4 distinct variants of the UCL, with approximately 23% of specimens containing an accessory ligament.[11]

Congenital radioulnar synostosis is a rare anomaly resulting from the failed segmentation and fusion of the radius and ulna. While flexion and extension remain unaffected, supination and pronation are restricted, potentially leading to compensatory strain on the shoulder and wrist.[12]

Surgical Considerations

Elbow injuries are highly prevalent in athletic populations. Consequently, efforts continuously focus on methods to enhance the strength and stability of the joint.

MCL tears are common in professional baseball players due to the extreme torque exerted on the elbow by pitching. Reconstruction of the MCL, commonly referred to as "Tommy John surgery," demonstrates a high success rate, with approximately 90% of patients returning to play.[13]

Medial epicondylitis, or golfer’s elbow, occurs frequently in older populations and results from repetitive flexion and valgus stress on the elbow. Initial management is typically conservative, including nonsteroidal anti-inflammatory drugs, ice, and corticosteroid injections. Cases refractory to conservative therapy may be addressed arthroscopically, with debridement of the common flexor tendon insertion at the medial epicondyle, thereby reducing stress on the medial structures and alleviating pain.[14]

Distal biceps tendon ruptures represent approximately 10% of all biceps injuries and typically result from a sudden extension force applied to a flexed elbow. Most cases involve complete avulsion of the tendon from the radial tuberosity, with tears of the bicipital aponeurosis occurring variably. Surgical reinsertion of the tendon onto the radial tuberosity is generally preferred, whereas nonoperative management may be considered in older adults. Clinical outcomes following operative repair are usually favorable.[15]

Osteochondritis dissecans of the elbow is marked by avascular necrosis of the articular cartilage and subchondral bone of the capitellum. This condition predominantly affects young athletes and may require surgical intervention, including debridement, drilling, microfracture, or fragment fixation, when conservative management fails.[16][17]

Additional surgical considerations for the elbow include treatment of osseous and ligamentous injuries associated with dislocation or blunt trauma. Minor procedures may also be indicated for inflammatory conditions such as bursitis.

Clinical Significance

Nursemaid's elbow is a common pediatric injury occurring in children aged 6 months to 5 years. Also referred to as "radial head subluxation," this condition typically results from an abrupt pulling force applied to the hand or forearm when the elbow is extended, causing displacement of the annular ligament. This band of connective tissue wraps around the head of the radius, securing the bone's connection to the ulna at the proximal radioulnar joint. In this injury, neither bone nor ligament is necessarily damaged. Instead, the ligament slips out of its normal position. Affected children present with acute pain and typically hold the arm against the body or on the lap, avoiding movement. Pain generally subsides quickly, although discomfort persists until reduction is achieved.

Management of radial head subluxation is noninvasive and may be performed in an outpatient setting. Two primary reduction techniques are employed. The supination-flexion method involves stabilizing the elbow while flexing the forearm to the shoulder and simultaneously supinating the arm until the joint is reduced.[18] The increasingly favored hyperpronation method may achieve higher 1st-time success rates, according to recent studies. Discomfort usually resolves following reduction, though analgesics such as acetaminophen may be administered for pain relief.[19]

Olecranon bursitis arises from trauma or prolonged pressure on the olecranon bursa. Bursitis can affect any bursa, but the olecranon bursa is among the most commonly involved. This bursa is superficial, located beneath the skin and overlying the triceps tendon and olecranon. The condition is sometimes referred to as "student elbow," as prolonged pressure, such as leaning on the elbows for extended periods, can provoke inflammation.

Olecranon bursitis may also occur as an idiopathic condition or develop as an infectious process, with trauma being the most frequent cause of infection. The diagnosis of septic bursitis is best confirmed by aspiration and culture of bursal fluid. Initial treatment is conservative, including nonsteroidal anti-inflammatory drugs, rest, compression, ice, and needle aspiration, which serves both diagnostic and therapeutic purposes. Operative intervention, such as olecranon bursectomy, is reserved for chronic cases that impair function.[20]

Elbow dislocations occur more frequently in athletes than in the general population, with the elbow representing the 2nd most commonly dislocated large joint after the shoulder. Simple dislocations should be managed promptly with range-of-motion exercises and gradual return to activity, including in high-level athletes. Complex dislocations, particularly those associated with fracture or ligamentous injury, or cases presenting with postinjury instability, may require surgical intervention. Posterior dislocations are often the most severe, producing extensive ligamentous damage. Standard evaluation includes obtaining anteroposterior and lateral radiographs before and after reduction, unless neurovascular compromise necessitates immediate intervention. Regardless of complexity, elbow dislocations should be reduced as soon as possible to restore joint alignment and function.

Other Issues

Iatrogenic nerve injuries during elbow surgery frequently result from inadvertent trauma during dissection, retraction, or improper incision placement in approaches such as Kocher (lateral), Hotchkiss (medial), or olecranon osteotomy (posterior). The posterior interosseous nerve is particularly susceptible during lateral extensions beyond 25 mm from the radiocapitellar joint or anterior Kaplan incisions due to supinator elevation. The ulnar nerve is at risk of traction injury during medial or posterior mobilizations without decompression, while the medial antebrachial cutaneous nerve may be injured during skin flap elevation.

Possible sequelae include forearm rotation deficits and impingement from posterior interosseous nerve injury, ulnar nerve–related weakness or instability, and sensory loss. These complications emphasize the importance of careful nerve protection and limited soft tissue dissection.[21]

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References

1.

Morris MS, Ozer K. Elbow Dislocations in Contact Sports. Hand Clin. 2017 Feb;33(1):63-72. [PubMed: 27886840]

2.

Downing M, Sergent SR. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 31, 2023. Anatomy, Shoulder and Upper Limb, Elbow Collateral Ligaments. [PubMed: 32809742]

3.

Chauhan M, Anand P, Das JM. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Aug 14, 2023. Cubital Tunnel Syndrome(Archived) [PubMed: 30855847]

4.

Aquilina AL, Grazette AJ. Clinical Anatomy and Assessment of the Elbow. Open Orthop J. 2017;11:1347-1352. [PMC free article: PMC5721323] [PubMed: 29290874]

5.

Al-Qattan MM, Yang Y, Kozin SH. Embryology of the upper limb. J Hand Surg Am. 2009 Sep;34(7):1340-50. [PubMed: 19700076]

6.

Mérida-Velasco JA, Sánchez-Montesinos I, Espín-Ferra J, Mérida-Velasco JR, Rodríguez-Vázquez JF, Jiménez-Collado J. Development of the human elbow joint. Anat Rec. 2000 Feb 01;258(2):166-75. [PubMed: 10645964]

7.

Cuadrado GA, de Andrade MFC, Akamatsu FE, Jacomo AL. Lymph drainage of the upper limb and mammary region to the axilla: anatomical study in stillborns. Breast Cancer Res Treat. 2018 Jun;169(2):251-256. [PubMed: 29380209]

8.

Stein JM, Cook TS, Simonson S, Kim W. Normal and variant anatomy of the elbow on magnetic resonance imaging. Magn Reson Imaging Clin N Am. 2011 Aug;19(3):609-19. [PubMed: 21816334]

9.

de Haan J, Schep NW, Eygendaal D, Kleinrensink GJ, Tuinebreijer WE, den Hartog D. Stability of the elbow joint: relevant anatomy and clinical implications of in vitro biomechanical studies. Open Orthop J. 2011;5:168-76. [PMC free article: PMC3104563] [PubMed: 21633722]

10.

Nihalani S, Frith K, Conklin M. Pediatric Supracondylar Process Fracture: Radiographic Distinction, Misdiagnosis, and Conservative Management. Cureus. 2024 Sep;16(9):e68547. [PMC free article: PMC11449195] [PubMed: 39364505]

11.

Acosta Batlle J, Cerezal L, López Parra MD, Alba B, Resano S, Blázquez Sánchez J. The elbow: review of anatomy and common collateral ligament complex pathology using MRI. Insights Imaging. 2019 Apr 03;10(1):43. [PMC free article: PMC6447645] [PubMed: 30945023]

12.

Tsai J. Congenital radioulnar synostosis. Radiol Case Rep. 2017 Sep;12(3):552-554. [PMC free article: PMC5551910] [PubMed: 28828125]

13.

Conte SA, Fleisig GS, Dines JS, Wilk KE, Aune KT, Patterson-Flynn N, ElAttrache N. Prevalence of Ulnar Collateral Ligament Surgery in Professional Baseball Players. Am J Sports Med. 2015 Jul;43(7):1764-9. [PubMed: 25925603]

14.

do Nascimento AT, Claudio GK. Arthroscopic surgical treatment of medial epicondylitis. J Shoulder Elbow Surg. 2017 Dec;26(12):2232-2235. [PubMed: 29054383]

15.

Schmidt CC, Styron JF, Lin EA, Brown BT. Distal Biceps Tendon Anatomic Repair. JBJS Essent Surg Tech. 2017 Dec 28;7(4):e32. [PMC free article: PMC6132996] [PubMed: 30233967]

16.

de Graaff F, Krijnen MR, Poolman RW, Willems WJ. Arthroscopic surgery in athletes with osteochondritis dissecans of the elbow. Arthroscopy. 2011 Jul;27(7):986-93. [PubMed: 21693350]

17.

Wood D, Davis DD, Carter KR. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Aug 8, 2023. Osteochondritis Dissecans. [PubMed: 30252347]

18.

Baiu I, Melendez E. Nursemaid's Elbow (Elbow Subluxation). JAMA. 2018 Feb 06;319(5):515. [PubMed: 29411033]

19.

Spiegel R, Kleist S. Hyperpronation Method for Reduction of Nursemaid's Elbow. Am Fam Physician. 2018 May 15;97(10):Online. [PubMed: 29763276]

20.

Reilly D, Kamineni S. Olecranon bursitis. J Shoulder Elbow Surg. 2016 Jan;25(1):158-67. [PubMed: 26577126]

21.

Aggarwal S, Paknikar K, Sinha J, Compson J, Reichert I. Comprehensive review of surgical approaches to the elbow. J Clin Orthop Trauma. 2021 Sep;20:101482. [PMC free article: PMC8254122] [PubMed: 34262848]

Disclosure: Ryan Card declares no relevant financial relationships with ineligible companies.

Disclosure: Jason Lowe declares no relevant financial relationships with ineligible companies.

Disclosure: Marjorie Launico declares no relevant financial relationships with ineligible companies.