Author: Nicola McLaren MSc•Reviewer: Dimitrios Mytilinaios MD, PhDLast reviewed: September 09, 2021Reading time: 15 minutes
The glenohumeral, or shoulder, joint is a synovial joint that attaches the top limb to the axial skeleton. It is a ball-and-socket joint, developed in between the glenoid fossa of scapula (gleno-) and also the head of humerus (-humeral).
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Acting in conjunction through the pectdental girdle, the shoulder joint allows for a vast array of activity at the top limb; flexion, expansion, abduction, adduction, external/lateral rotation, internal/medial rotation and circumduction. In truth, it is the the majority of mobile joint of the huguy body. This shoulder feature comes at the price of stability however, as the bony surfaces market bit support. Instead the surrounding shoulder muscles and ligamentous structures offer the joint security; the capsule, ligaments and also tendons of the rotator cuff muscles. Therefore mobility-stability damage, the shoulder joint is just one of the the majority of generally injured joints of the body.
|Type||Synovial ball and also socket joint; multiaxial|
|Articular surfaces||Glenoid fossa of scapula, head of humerus; glenoid labrum|
|Ligaments||Superior glenohumeral, middle glenohumeral, inferior glenohumeral, coracohumeral, transverse humeral|
|Innervation||Subscapular nerve (joint); suprascapular nerve, axillary nerve, lateral pectoral nerve (joint capsule)|
|Blood supply||Anterior and also posterior circumflex humeral, circumflex scapular and suprascapular arteries|
|Movements||Flexion, extension, abduction, adduction, external/lateral rotation, internal/medial rotation and also circumduction|
|Rotator cuff muscles||Supraspinatus, infraspinatus, teres minor, subscapularis Mnemonic: Rotator cuff SITS on the shoulder|
This short article will discuss the anatomy and function of the glenohumeral joint.
The glenohumeral joint is the articulation in between the spherical head of the humerus and the concave glenoid fossa of the scapula. Being a synovial joint, both articular surfaces are covered via hyaline cartilage.
The glenoid fossa is a shallow pear-shaped pit on the superolateral angle of scapula. The concavity of the fossa is much less acute than the convexity of the humeral head, interpretation that the articular surencounters are not fully congruent. Congruency is raised rather by the visibility of a glenoid labrum, a fibrocartilaginous ring that attaches to the margins of the fossa. The labrum acts to deepen the glenoid fossa slightly, it is triangular in shape and also thicker anteriorly than inferiorly. The surface of the humeral head is three to 4 times larger than the surconfront of glenoid fossa, interpretation that only a 3rd of the humeral head is ever in contact through the fossa and labrum.
This incongruent bony anatomy permits for the wide range of activity available at the shoulder joint however is also the reason for the absence of joint stcapacity. Instead, joint protection is offered totally by the soft tissue structures; the fibrous capsule, ligaments, shoulder muscles and their tendons.
The shoulder joint is encircled by a loosened fibrous capsule. It extends from the scapula to the humerus, encshedding the joint on all sides. The internal surconfront of the capsule is lined by a synovial membrane.
On the humerus, the capsule attaches to its anatomical neck. Extending only at its medial margin, wright here the fibers protrude by approximately 1 cm. On the scapula, the capsule has actually 2 lines of attachments. The first is on its anterior and also inferior sides wbelow the capsule inserts into the scapular neck, posterior to the glenoid labrum. The second is on its superior and also posterior aspects, wbelow the capsular fibers blend straight through the glenoid labrum. Here the capsule arches over the supraglenoid tubercle and also it’s long head of biceps brachii muscle attachment, thus making these intra-articular frameworks.
The capsule remains lax to permit for mobility of the top limb. It relies on ligaments and muscle tendons to carry out reinforcement. The anterior capsule is thickened by the 3 glenohumeral ligaments while the tendons of the rotator cuff muscles spcheck out over the capsule blfinishing through its outside surface. These tendons form a continuous spanning dubbed the rotator capsule. It is consisted of of the supraspinatus superiorly, infraspinatus and also teres minor posteriorly, subscapularis anteriorly and the lengthy head of triceps brachii inferiorly.
Two weak spots exist in this reincompelled capsule. The initially is the rotator interval, a space of unreinrequired capsule that exists in between the subscapularis and supraspinatus tendons. The second is the inferior capsular aspect, this is the suggest wright here the capsule is the weakest. The loose inferior capsule forms a fold when the arm is in the anatomical position. It becomes extended, and leastern sustained, once the arm is abducted.
The capsule has actually two openings;Between the better and lesser tubercles of humerus, through which the tendon of the lengthy head of biceps brachii passes.Between the remarkable and also middle glenohumeral ligaments, via which the subscapular bursa communicates via the glenohumeral joint cavity.
Synovial fluid filled bursae help with the joint’s mobility. The subdeltoid-subacromial (SASD) bursa is situated between the joint capsule and the deltoid muscle or acromion, respectively. Similarly the subcoracoid bursae are discovered in between the capsule and also the coracoid procedure of the scapula. The subscapular bursa sits between the capsule and the subscapularis tendon, while the coracobrachial bursa is located between the subscapularis and also coracobrachialis muscles. These bursae allow the structures of the shoulder joint to slide easily over one another.
Jump right right into the anatomy of the glenohumeral joint with this incorporated quiz:
Explore our video tutorials, quizzes, short articles and also atlas imperiods of glenohumeral joint for a full understanding of its anatomy.
Several ligaments limit the movement of the GH joint and stand up to humeral dislocation. These are the coracohumeral, glenohumeral and transverse humeral ligaments. Glenohumeral and transverse humeral are capsular ligaments while coracohumeral is an accessory ligament.
The transverse humeral ligament exoften tends horizontally in between the tubercles of the humerus. It covers the intertubercular sulcus and the lengthy head tendon of the biceps brachii muscle, avoiding displacement of the tendon from the sulcus. The coracohumeral ligament exhas a tendency between the coracoid procedure of the scapula to the tubercles of the humerus and also the intervening transverse humeral ligament, sustaining the joint from its remarkable side. It acts to limit inferior translation and also too much external rotation of the humerus.
The premium, middle and inferior glenohumeral ligaments support the joint from the anteroinferior side. They have a weak stabilizing function, each acting to limit the maximum amplitude of particular arm movements;All three ligaments become taut in the time of external (lateral) rotation of humerus, while they relax in internal (medial) rotation. They additionally stand up to anterior translation of the humeral head. The middle and inferior ligaments tense throughout abduction, while the remarkable is tranquil.
The remarkable glenohumeral ligament exhas a tendency from the supraglenoid tubercle of scapula to the proximal element of the lesser tubercle of humerus. Along via the coracohumeral ligament, it supports the rotator interval and stays clear of inferior translation of the humeral head, specifically throughout shoulder adduction.
The middle glenohumeral ligament attaches alengthy the anterior glenoid margin of the scapula, just inferior to the superior GH ligament. It exoften tends to the lesser tubercle of humerus. This wide ligament lies deep to, and also blends, via the tendon of subscapularis muscle. It stabilizes the anterior capsule, limiting external rotation, particularly when the arm is in an abducted position (45o – 60o abduction).
The inferior glenohumeral ligament is a sling-choose ligament extfinishing in between the glenoid labrum and also the inferomedial part of the humeral neck. It is split into anterior and posterior bands, in between which sits the axillary pouch. This is the strongest of the three GH ligaments, being thicker and also longer than the other 2. Both bands stabilize the humeral head once the arm is abducted over 90°. The anterior band borders external rotation of the arm, while the posterior band borders internal rotation.
The glenohumeral joint is innervated by the subscapular nerve (C5-C6), a branch of the posterior cord of brachial plexus. The joint capsule is offered from several sources;Lateral pectoral nerve offers the anterosuperior component and also the rotator capsule
Blood supply to the shoulder joint comes from the anterior and posterior circumflex humeral, circumflex scapular and also suprascapular arteries.
The glenohumeral joint has a greater array of activity (RoM) than any type of various other body joint. Being a ball-and-socket joint, it enables activities in three levels of freedom (average maximum glenohumeral active RoM is shown in brackets);Flexion (110°) - expansion (60°)Abduction (120°) - adduction (0°)Internal rotation (90°) - exterior rotation (90°)
Combicountry of these activities gives circumduction.
Activities of the arm rely on movement from not only the glenohumeral joint yet likewise the scapulothoracic joint (acromioclavicular, sternoclavicular and scapulothoracic articulations). With Each Other these joints have the right to change the place of the glenoid fossa, loved one to the chest wall. Thus repositioning the glenohumeral joint, and also upper limb, within area. This provides for a better range of activity easily accessible within the greater shoulder complex;Flexion (180°) - extension (90°)Abduction (180°) - adduction (30°)Internal rotation (90°) - External rotation (90°)
The close-packed place of the glenohumeral joint is abduction and external rotation, while open packed (resting) position is abduction (40-50°) with horizontal adduction (30°). The joints’ capsular pattern is external rotation, adhered to by abduction, internal rotation and flexion. The added accessory motions of spin, roll and slide (glide) are additionally obtainable within the glenohumeral joint.
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Muscles acting on the shoulder joint
The scapulohumeral and also thoracohumeral muscles are responsible for developing activity at the glenohumeral joint.
|Flexion||Pectoralis significant, deltoid, coracobrachialis, lengthy head of biceps brachii|
|Extension||Latissimus dorsi, teres significant, pectoralis significant, deltoid, long head of triceps brachii|
|Adduction||Coracobrachialis, pectoralis significant, latissimus dorsi, teres major|
|Internal rotation||Subscapularis, teres significant, latissimus dorsi, pectoralis significant, deltoid|
|External rotation||Teres minor, infraspinatus, deltoid|
The prime flexors of the glenohumeral joint are the deltoid (anterior fibers) and also pectoralis significant (clavicular fibers) muscles. While coracobrachialis and the long head of biceps brachii help as weak flexor muscles.
Extension is performed by the latissimus dorsi, teres significant, pectoralis significant (sternocostal fibers) and also lengthy head of triceps brachii muscles. Of note, is that these muscles have actually a stronger activity when acting to extfinish the flexed arm.
The prime abductors of the arm are the supraspinatus and also deltoid muscles. Traditionally it was believed that supraspinatus was essential for movement initiation and also early abduction, while the deltoid muscle involved from about 20° of abduction and also carried the arm through to the full 180° of abduction. However before even more recent evidence has actually suggested that both muscles are set off via all parts of the abduction activity. Contraction of the deltoid muscle uses a solid exceptional translation force to the humerus, this is countered by the activity of the rotator cuff muscles, preventing remarkable humeral dislocation.
Adduction is produced by the pectoralis major, latissimus dorsi and teres significant muscles. Together these three are well-known as the “climbing muscles”, as they are effective adductors, alternatively they deserve to lift the trunk up towards a addressed arm. The coracobrachialis, teres minor, brief head of biceps, long head of triceps brachii and deltoid (posterior fibers) muscles are likewise active in the time of this movement, depending upon the position of the arm. In certain, accessory adductor muscles serve to respond to the solid internal rotation created by pectoralis major and latissimus dorsi.
Internal rotation is mainly percreated by the subscapularis and also teres major muscles. Pectoralis major, deltoid (anterior fibers) and also latissimus dorsi are likewise capable of creating this motion. The major lateral rotators are the infraspinatus and also teres minor muscles, via aid from the posterior fibers of the deltoid muscle. External rotation of the humerus moves the higher tubercle out from under the acromial arch, allowing uninhibited arm abduction to take place.
The rotator cuff muscles are four muscles that form a musculotendinous unit about the shoulder joint. These are the supraspinatus, infraspinatus, teres minor and subscapularis muscles. The function of this entire muscular apparatus is to create movement at the shoulder joint while keeping the head of humerus stable and centralized within the glenoid cavity.
Memorize the rotator cuff muscles using the mnemonic given below!
Rotator cuff SITS on the shoulderSupraspinatusInfraspinatusTeres minorSubscapularis
All 4 muscles are firmly attached approximately the joint in such a way that they form a sleeve (rotator capsule). Individually, each muscle has its own pulling axis that results in a specific movement (prime mover), while together they produce a concavity compression. This is a stabilizing device in which compression of the humerus right into the concavity of glenoid fossa avoids its dislocation by translating forces.
Take the complying with practice quiz for a rotator cuff workout! You have the right to even add and also rerelocate individual muscles if you favor.
References:Cael, C. (2010). Functional anatomy: Musculoskeletal anatomy, kinesiology, and palpation for hands-on therapists. Philadelphia, PA: Wolters Kluwer Health/Lippincott, Williams & Wilkins.Hall, S. J. (2015). Basic biomechanics (7th ed.). New York, NY: McGraw-Hill EducationMagee, D. J. (2014). Orthopedic physical assessment (6th ed.). St. Louis: Elsevier Saunders.Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.Netter, F. (2019). Atlas of Person Anatomy (7th ed.). Philadelphia, PA: Saunders.Palastanga, N., & Soames, R. (2012). Anatomy and human movement: framework and also feature (sixth ed.). Edinburgh: Churchill Livingrock.Richards, J. (2018). The detailed textbook of clinical biomechanics (second ed.). Amsterdam, The Netherlands: Elsevier.Standring, S. (2016). Gray"s Anatomy (41tst ed.). Edinburgh: Elsevier Churchill Livingstone.
Glenohumeral joint (Articulatio glenohumeralis) - Yousun Koh
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