The elbow is the region between the upper arm and the forearm that surrounds the elbow joint.[1] The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the medial epicondyles of the humerus. The elbow joint is a hinge joint between the arm and the forearm;[2] more specifically between the humerus in the upper arm and the radius and ulna in the forearm which allows the forearm and hand to be moved towards and away from the body.[3][4]The term elbow is specifically used for humans and other primates, and in other vertebrates it is not used. In those cases, forelimb plus joint is used.[1]
The name for the elbow in Latin is cubitus, and so the word cubital is used in some elbow-related terms, as in cubital nodes for example.
The elbow joint has three different portions surrounded by a common joint capsule. These are joints between the three bones of the elbow, the humerus of the upper arm, and the radius and the ulna of the forearm.
When in anatomical position there are four main bony landmarks of the elbow. At the lower part of the humerus are the medial and lateral epicondyles, on the side closest to the body (medial) and on the side away from the body (lateral) surfaces. The third landmark is the olecranon found at the head of the ulna. These lie on a horizontal line called the Hueter line. When the elbow is flexed, they form a triangle called the Hueter triangle, which resembles an equilateral triangle.[5]
At the surface of the humerus where it faces the joint is the trochlea. In most people, the groove running across the trochlea is vertical on the anterior side but it spirals off on the posterior side. This results in the forearm being aligned to the upper arm during flexion, but forming an angle to the upper arm during extension — an angle known as the carrying angle.[6]
The superior radioulnar joint shares the joint capsule with the elbow joint but plays no functional role at the elbow.[7]
The elbow joint and the superior radioulnar joint are enclosed by a single fibrous capsule. The capsule is strengthened by ligaments at the sides but is relatively weak in front and behind.[8]
On the anterior side, the capsule consists mainly of longitudinal fibres. However, some bundles among these fibers run obliquely or transversely, thickening and strengthening the capsule. These bundles are referred to as the capsular ligament. Deep fibres of the brachialis muscle insert anteriorly into the capsule and act to pull it and the underlying membrane during flexion in order to prevent them from being pinched.[8]
On the posterior side, the capsule is thin and mainly composed of transverse fibres. A few of these fibres stretch across the olecranon fossa without attaching to it and form a transverse band with a free upper border. On the ulnar side, the capsule reaches down to the posterior part of the annular ligament. The posterior capsule is attached to the triceps tendon which prevents the capsule from being pinched during extension.[8]
The synovial membrane of the elbow joint is very extensive. On the humerus, it extends up from the articular margins and covers the coronoid and radial fossae anteriorly and the olecranon fossa posteriorly. Distally, it is prolonged down to the neck of the radius and the superior radioulnar joint. It is supported by the quadrate ligament below the annular ligament where it also forms a fold which gives the head of the radius freedom of movement.[8]
Several synovial folds project into the recesses of the joint.[8]These folds or plicae are remnants of normal embryonic development and can be categorized as either anterior (anterior humeral recess) or posterior (olecranon recess).[9]A crescent-shaped fold is commonly present between the head of the radius and the capitulum of the humerus.[8]
On the humerus there are extrasynovial fat pads adjacent to the three articular fossae. These pads fill the radial and coronoid fossa anteriorly during extension, and the olecranon fossa posteriorly during flexion. They are displaced when the fossae are occupied by the bony projections of the ulna and radius.[8]
The elbow, like other joints, has ligaments on either side. These are triangular bands which blend with the joint capsule. They are positioned so that they always lie across the transverse joint axis and are, therefore, always relatively tense and impose strict limitations on abduction, adduction, and axial rotation at the elbow.[8]
The ulnar collateral ligament has its apex on the medial epicondyle. Its anterior band stretches from the anterior side of the medial epicondyle to the medial edge of the coronoid process, while the posterior band stretches from posterior side of the medial epicondyle to the medial side of the olecranon. These two bands are separated by a thinner intermediate part and their distal attachments are united by a transverse band below which the synovial membrane protrudes during joint movements. The anterior band is closely associated with the tendon of the superficial flexor muscles of the forearm, even being the origin of flexor digitorum superficialis. The ulnar nerve crosses the intermediate part as it enters the forearm.[8]
The radial collateral ligament is attached to the lateral epicondyle below the common extensor tendon. Less distinct than the ulnar collateral ligament, this ligament blends with the annular ligament of the radius and its margins are attached near the radial notch of the ulna.[8]
There are three main flexor muscles at the elbow:[10]
Brachialis is the main muscle used when the elbow is flexed slowly. During rapid and forceful flexion all three muscles are brought into action assisted by the superficial forearm flexors originating at the medial side of the elbow.[11]The efficiency of the flexor muscles increases dramatically as the elbow is brought into midflexion (flexed 90°) — biceps reaches its angle of maximum efficiency at 80–90° and brachialis at 100–110°.[10]
Active flexion is limited to 145° by the contact between the anterior muscles of the upper arm and forearm, more so because they are hardened by contraction during flexion. Passive flexion (forearm is pushed against the upper arm with flexors relaxed) is limited to 160° by the bony projections on the radius and ulna as they reach to shallow depressions on the humerus; i.e. the head of radius being pressed against the radial fossa and the coronoid process being pressed against the coronoid fossa. Passive flexion is further limited by tension in the posterior capsular ligament and in triceps brachii.[12]
A small accessory muscle, so called epitrochleoanconeus muscle, may be found on the medial aspect of the elbow running from the medial epicondyle to the olecranon.[13]
Elbow extension is simply bringing the forearm back to anatomical position.[11] This action is performed by triceps brachii with a negligible assistance from anconeus. Triceps originates with two heads posteriorly on the humerus and with its long head on the scapula just below the shoulder joint. It is inserted posteriorly on the olecranon.[10]
Triceps is maximally efficient with the elbow flexed 20–30°. As the angle of flexion increases, the position of the olecranon approaches the main axis of the humerus which decreases muscle efficiency. In full flexion, however, the triceps tendon is "rolled up" on the olecranon as on a pulley which compensates for the loss of efficiency. Because triceps' long head is biarticular (acts on two joints), its efficiency is also dependent on the position of the shoulder.[10]
Extension is limited by the olecranon reaching the olecranon fossa, tension in the anterior ligament, and resistance in flexor muscles. Forced extension results in a rupture in one of the limiting structures: olecranon fracture, torn capsule and ligaments, and, though the muscles are normally left unaffected, a bruised brachial artery.[12]
The arteries supplying the joint are derived from an extensive circulatory anastomosis between the brachial artery and its terminal branches. The superior and inferior ulnar collateral branches of the brachial artery and the radial and middle collateral branches of the profunda brachii artery descend from above to reconnect on the joint capsule, where they also connect with the anterior and posterior ulnar recurrent branches of the ulnar artery; the radial recurrent branch of the radial artery; and the interosseous recurrent branch of the common interosseous artery.[14]
The blood is brought back by vessels from the radial, ulnar, and brachial veins. There are two sets of lymphatic nodes at the elbow, normally located above the medial epicondyle — the deep and superficial cubital nodes (also called epitrochlear nodes). The lymphatic drainage at the elbow is through the deep nodes at the bifurcation of the brachial artery, the superficial nodes drain the forearm and the ulnar side of the hand. The efferent lymph vessels from the elbow proceed to the lateral group of axillary lymph nodes.[14][15]
The elbow is innervated anteriorly by branches from the musculocutaneous, median, and radial nerve, and posteriorly from the ulnar nerve and the branch of the radial nerve to anconeus.[14]
The elbow undergoes dynamic development of ossification centers through infancy and adolescence, with the order of both the appearance and fusion of the apophyseal growth centers being crucial in assessment of the pediatric elbow on radiograph, in order to distinguish a traumatic fracture or apophyseal separation from normal development. The order of appearance can be understood by the mnemonic CRITOE, referring to the capitellum, radial head, internal epicondyle, trochlea, olecranon, and external epicondyle at ages 1, 3, 5, 7, 9 and 11 years. These apophyseal centers then fuse during adolescence, with the internal epicondyle and olecranon fusing last. The ages of fusion are more variable than ossification, but normally occur at 13, 15, 17, 13, 16 and 13 years, respectively.[16] In addition, the presence of a joint effusion can be inferenced by the presence of the fat pad sign, a structure that is normally physiologically present, but pathologic when elevated by fluid, and always pathologic when posterior.[17]
The function of the elbow joint is to extend and flex the arm.[18] The range of movement in the elbow is from 0 degrees of elbow extension to 150 degrees of elbow flexion.[19] Muscles contributing to function are all flexion (biceps brachii, brachialis, and brachioradialis) and extension muscles (triceps and anconeus).
In humans, the main task of the elbow is to properly place the hand in space by shortening and lengthening the upper limb. While the superior radioulnar joint shares joint capsule with the elbow joint, it plays no functional role at the elbow.[7]
With the elbow extended, the long axis of the humerus and that of the ulna coincide.[20] At the same time, the articular surfaces on both bones are located in front of those axes and deviate from them at an angle of 45°.[21] Additionally, the forearm muscles that originate at the elbow are grouped at the sides of the joint in order not to interfere with its movement. The wide angle of flexion at the elbow made possible by this arrangement — almost 180° — allows the bones to be brought almost in parallel to each other.[7]
When the arm is extended, with the palm facing forward or up, the bones of the upper arm (humerus) and forearm (radius and ulna) are not perfectly aligned. The deviation from a straight line occurs in the direction of the thumb, and is referred to as the "carrying angle".[22]
The carrying angle permits the arm to be swung without contacting the hips. Women on average have smaller shoulders and wider hips than men, which tends to produce a larger carrying angle (i.e., larger deviation from a straight line than that in men). There is, however, extensive overlap in the carrying angle between individual men and women, and a sex-bias has not been consistently observed in scientific studies.[23]
The angle is greater in the dominant limb than the non-dominant limb of both sexes,[24] suggesting that natural forces acting on the elbow modify the carrying angle. Developmental,[25] aging and possibly racial influences add further to the variability of this parameter.
The types of disease most commonly seen at the elbow are due to injury.
Two of the most common injuries at the elbow are overuse injuries: tennis elbow and golfer's elbow.[26] Golfer's elbow involves the tendon of the common flexor origin which originates at the medial epicondyle of the humerus (the "inside" of the elbow).[26] Tennis elbow is the equivalent injury, but at the common extensor origin (the lateral epicondyle of the humerus).[26]
There are three bones at the elbow joint, and any combination of these bones may be involved in a fracture of the elbow. Patients who are able to fully extend their arm at the elbow are unlikely to have a fracture (98% certainty) and an X-ray is not required as long as an olecranon fracture is ruled out.[27] Acute fractures may not be easily visible on X-ray.[28]
Elbow dislocations constitute 10% to 25% of all injuries to the elbow. The elbow is one of the most commonly dislocated joints in the body, with an average annual incidence of acute dislocation of 6 per 100,000 persons.[30] Among injuries to the upper extremity, dislocation of the elbow is second only to a dislocated shoulder. A full dislocation of the elbow will require expert medical attention to re-align, and recovery can take approximately 6 weeks.[citation needed]
Infection of the elbow joint (septic arthritis) is uncommon. It may occur spontaneously, but may also occur in relation to surgery or infection elsewhere in the body (for example, endocarditis).[31]
Elbow arthritis is usually seen in individuals with rheumatoid arthritis or after fractures that involve the joint itself. When the damage to the joint is severe, fascial arthroplasty or elbow joint replacement may be considered.[32]
Olecranon bursitis, tenderness, warmth, swelling, pain in both flexion and extension-in chronic case great flexion-is extremely painful.
Elbow pain occurs when the tenderness of the tissues in the elbow become inflamed. Frequent exercise of the inflamed elbow will assist with healing.
Elbow pain can occur for a multitude of reasons, including injury, disease, and other conditions. Common conditions include tennis elbow, golfer's elbow, distal radioulnar joint rheumatoid arthritis, and cubital tunnel syndrome.
Теннисный локоть — очень распространенный тип травмы от перенапряжения. Оно может возникнуть как от хронических повторяющихся движений кисти и предплечья, так и от травмы тех же областей. Эти повторения могут повредить сухожилия, которые соединяют мышцы-разгибатели-супинаторы (которые вращают и разгибают предплечье) с локтевым отростком (также известным как «локоть»). Возникает боль, часто иррадиирующая из латеральной поверхности предплечья. Также очень распространены слабость, онемение и скованность, а также болезненность при прикосновении. [33] Неинвазивным методом лечения боли является отдых. Если достижение покоя является проблемой, можно также надеть бандаж на запястье. Это удерживает запястье в согнутом состоянии, тем самым разгружая мышцы-разгибатели и позволяя отдохнуть. Лед, тепло, ультразвук, инъекции стероидов и компрессия также могут помочь облегчить боль. После того, как боль уменьшилась, важна лечебная физкультура, чтобы предотвратить травмы в будущем. Упражнения должны быть с низкой скоростью, а вес должен постепенно увеличиваться. [34] Полезны растяжка сгибателей и разгибателей, а также укрепляющие упражнения. Также может быть полезен массаж, направленный на триггерные точки разгибателей . [35]
Локоть гольфиста очень похож на локоть теннисиста, но встречается реже. Это вызвано чрезмерным использованием и повторяющимися движениями, такими как свинг в гольфе. Это также может быть вызвано травмой. Сгибание и пронация запястья (вращение предплечья) вызывают раздражение сухожилий вблизи медиального надмыщелка локтя. [36] Это может вызвать боль, скованность, потерю чувствительности и слабость, иррадиирующую от внутренней части локтя к пальцам. Отдых является основным вмешательством при этой травме. Также могут помочь лед, обезболивающие, инъекции стероидов, укрепляющие упражнения и отказ от любых отягчающих действий. Хирургическое вмешательство является крайней мерой и применяется редко. Упражнения должны быть направлены на укрепление и растяжку предплечий, а также на использование правильной техники при выполнении движений. [37]
Ревматоидный артрит – хроническое заболевание, поражающее суставы. Это заболевание очень часто встречается в запястье и чаще всего в лучелоктевом суставе . Это приводит к боли, скованности и деформации. Существует много различных методов лечения ревматоидного артрита, и нет единого мнения о том, какой метод лучше. Наиболее распространенные методы лечения включают наложение шин на запястья, хирургическое вмешательство, физиотерапию и трудотерапию, а также противоревматические препараты . [38]
Синдром кубитального канала, более известный как локтевая невропатия , возникает, когда локтевой нерв раздражается и воспаляется. Это часто может произойти там, где локтевой нерв расположен наиболее поверхностно, в локтевом суставе. Локтевой нерв проходит над локтем в области, известной как «смешная кость». Раздражение может возникнуть из-за постоянного, повторяющегося стресса и давления в этой области или из-за травмы. Это также может произойти из-за деформации костей, а часто и из-за занятий спортом. [39] Симптомы включают покалывание, онемение и слабость, а также боль. Методы лечения боли первой линии включают использование нестероидных противовоспалительных препаратов для перорального применения . Они помогают уменьшить воспаление, давление и раздражение нерва и вокруг него. Другие простые решения включают в себя приобретение более эргономичных привычек, которые помогут предотвратить защемление и раздражение нервов в будущем. Защитное оборудование также может быть очень полезным. Примерами этого являются защитные налокотники и шины для рук. Более серьезные случаи часто включают хирургическое вмешательство, при котором нерв или окружающие ткани перемещаются, чтобы уменьшить давление. Восстановление после операции может занять некоторое время, но прогноз часто хороший. Восстановление часто включает ограничение движений и диапазона двигательной активности и может длиться несколько месяцев (синдром кубитального и радиального туннеля, 2).
Устаревшая единица длины элль тесно связана с локтем. Это становится особенно заметно, если принять во внимание германское происхождение обоих слов: Elle (ell, определяемый как длина мужского предплечья от локтя до кончиков пальцев) и Ellbogen (локоть). Неизвестно, когда и почему вторая буква «l» была исключена из английского употребления этого слова. [ нужна цитата ] Элль , как и в английской мере, также может происходить от буквы L, согнутой под прямым углом, как локоть. [40] Элль в качестве меры был принят в шесть ладоней; три до локтя и три от локтя до плеча. [41] Другой мерой был локоть (от cubital ). За эту величину принимали длину мужской руки от локтя до конца среднего пальца. [42]
Слова wenis и wagin в шутку используются для описания задней и передней областей локтя соответственно. Эти термины вошли в жаргонный лексикон в 1990-х годах и распространились как интернет-мем. [43] В частности, венис относится к рыхлому лоскуту кожи под локтем, а влагалище — к кожной складке локтевой ямки . [44]
Though the elbow is similarly adapted for stability through a wide range of pronation-supination and flexion-extension in all apes, there are some minor differences. In arboreal apes such as orangutans, the large forearm muscles originating on the epicondyles of the humerus generate significant transverse forces on the elbow joint. The structure to resist these forces is a pronounced keel on the trochlear notch on the ulna, which is more flattened in, for example, humans and gorillas. In knuckle-walkers, on the other hand, the elbow has to deal with large vertical loads passing through extended forearms and the joint is therefore more expanded to provide larger articular surfaces perpendicular to those forces.[45]
Derived traits in catarrhini (apes and Old World monkeys), elbows include the loss of the entepicondylar foramen (a hole in the distal humerus), a non-translatory (rotation-only) humeroulnar joint, and a more robust ulna with a shortened trochlear notch.[46]
The proximal radioulnar joint is similarly derived in higher primates in the location and shape of the radial notch on the ulna; the primitive form being represented by New World monkeys, such as the howler monkey, and by fossil catarrhines, such as Aegyptopithecus. In these taxa, the oval head of the radius lies in front of the ulnar shaft so that the former overlaps the latter by half its width. With this forearm configuration, the ulna supports the radius and maximum stability is achieved when the forearm is fully pronated.[46]
