Glenohumeral joint
Encyclopedia
The glenohumeral joint, (from ancient Greek glene, eyeball, puppet, doll + -oid, 'form of', + Latin humerus, shoulder) or shoulder joint, is a multiaxial synovial
ball and socket joint
and involves articulation between the glenoid fossa
of the scapula
(shoulder blade) and the head of the humerus (upper arm bone). Due to the very limited interface of the humerus and scapula, it is the most mobile joint of the human body.
Scapulohumeral rhythm helps to achieve further range of movement. The Scapulohumeral rhythm is the movement of the scapula across the thoracic cage in relation to the humerus. This movement can be compromised by anything that changes the position of the scapula. This could be an imbalance in the muscles that hold the scapula in place which are the upper and lower trapezium. This imbalance could cause a forward head carriage which in turn can affect the range of movements of the shoulder.
The rotator cuff
muscles of the shoulder produce a high tensile force, and help to pull the head of the humerus into the glenoid fossa.
that is lax inferiorly and therefore is at risk of dislocation
inferiorly. The long head of the biceps brachii muscle
travels inside the capsule to attach to the supraglenoid tubercle
of the scapula.
Because the tendon is inside the capsule, it requires a synovial tendon sheath to minimize friction.
A number of bursae
in the capsule aid mobility. Namely, they are the subdeltoid bursa (between the joint capsule and deltoid muscle), subcoracoid bursa (between joint capsule and coracoid process of scapula
), coracobrachial bursa (between subscapularis muscle and tendon of coracobrachialis muscle), subacromial bursa (between joint capsule and acromion of scapula) and the subscapular bursa (between joint capsule and tendon of subscapularis muscle
, also known as subtendinous bursa of subscapularis muscle). The bursa are formed by the synovial membrane of the joint capsule. An inferior pouching of the joint capsule between teres minor and subscapularis is known as the axillary recess.
The shoulder joint is a muscle dependent joint as it lacks strong ligaments.
) growing between the joint surfaces, causing pain and restricting movement of the shoulder, a condition known as frozen shoulder
or adhesive capsulitis.
Bigliani proclaimed 3 types:
The transversal stratification from the lower edge of the acromion up to the lower edge of the glenoid fossa is mandatory in order to depict changes of the glenoid labrum. Furthermore are oblique coronal or oblique sagittal planes not necessary examinations. Yet can they help to depict precisely the rotator cuff or the shape of the humeral head.
1. The sublabral superior recess:
Linear inflow of contrast agent between labrum and glenoid at the paracoronal sequence. Typically straightened medially towards the tuberculum supraglenoidale. The superior labrum often isn’t completely attached to the glenoid. There can be a variously deep sulcus which communicates with the joint cavity.
This anatomical variation is depictable at the 12 o’clock position in the oblique sagittal MR projection and can be subdivided into 3 types.
Park et al. examined 95 asymptomatic shoulders using MRA and was able to demonstrate a recess in 30% of the cases.
2. The sublabral foramen:
It can be found in around 11% of the cases and should not be confused with a sublabral superior recess. The range of the foramen is large. From only few millimeters up to a complete ablation of the antero-superior labrum. In contrast to the sublabral superior recess, is the sublabral superior foramen depictable in the oblique sagittal projection, positioned antero-superiorly at around 2 o’clock. And Inflow of contrast agent can be seen at the axial sequence between labrum and glenoid. It can sometimes be found combined with a sublabral superior recess. Enhanced MR imaging via an intraarticular contrast agent injection, can lead to a false positive interpretation as a labral injury. This variation of the norm is positioned antero-superiorly. Bankart lesions for example have an antero-inferior localisation.
3. The Buford complex:
The Buford complex can be found in 1.5% of the population. It consists of a ribbon-like thickening of the medial gleno-humeral ligament (GHL) and is further characterized by a lack of anterior superior labrum. The medial GHL inserts just at the area of the antero-superior glenoid. A thickened medial GHL can be confused with a displaced labral fragment on the arthroscope.
And furthermore:
4. In 50% of the cases a triangular linear signal increasement can be found at the area of the anterior labrum through hyaline cartilage. This is the most common shape and accounts for 73% in the posterior area and for 45% in the anterior area.
5. In 20% of the cases the labrum is rounded.
6. In 7% of the cases the labrum is comma-shaped flattened.
7. In 15% of the cases the labrum is splitted.
8. In 8% of the cases the labrum is notched.
9. The labrum has a central signal increasement.
10. The labrum has a linear signal increasement.
The fibers of the long biceps tendon irradiate in different forms into the labrum. Subdivided into an anterior and a posterior rein. After Vangsness et al. there are 4 types, of which type 2 is the most common.
Synovial joint
A Synovial joint, also known as a diarthrosis, is the most common and most movable type of joint in the body of a mammal. As with most other joints, synovial joints achieve movement at the point of contact of the articulating bones....
ball and socket joint
Ball and socket joint
A ball and socket joint is a joint in which the distal bone is capable of motion around an indefinite number of axes, which have one common center...
and involves articulation between the glenoid fossa
Glenoid cavity
The glenoid cavity is a shallow pyriform, articular surface, which is located on the lateral angle of the scapula. It is directed laterally and forward and articulates with the head of the humerus; it is broader below than above and its vertical diameter is the longest.This cavity forms the...
of the scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
(shoulder blade) and the head of the humerus (upper arm bone). Due to the very limited interface of the humerus and scapula, it is the most mobile joint of the human body.
Movements
The glenoid fossa is shallow and contains the glenoid labrum which deepens it and aids in stability. With 120 degrees of unassisted flexion, the glenohumeral joint is the most mobile joint in the body.Scapulohumeral rhythm helps to achieve further range of movement. The Scapulohumeral rhythm is the movement of the scapula across the thoracic cage in relation to the humerus. This movement can be compromised by anything that changes the position of the scapula. This could be an imbalance in the muscles that hold the scapula in place which are the upper and lower trapezium. This imbalance could cause a forward head carriage which in turn can affect the range of movements of the shoulder.
The rotator cuff
Rotator cuff
In anatomy, the rotator cuff is the group of muscles and their tendons that act to stabilize the shoulder. The four muscles of the rotator cuff, along with the teres major muscle, the coracobrachialis muscle and the deltoid, make up the seven scapulohumeral muscles of the human body.-Function:The...
muscles of the shoulder produce a high tensile force, and help to pull the head of the humerus into the glenoid fossa.
| Movement | Muscles | Origin | Insertion |
|---|---|---|---|
| Flexion Flexion In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder... (150°–170°) |
Anterior fibers of deltoid Deltoid muscle In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the central... |
Clavicle Clavicle In human anatomy, the clavicle or collar bone is a long bone of short length that serves as a strut between the scapula and the sternum. It is the only long bone in body that lies horizontally... |
Middle of lateral surface of shaft of humerus Body of humerus The body or shaft of the humerus is almost cylindrical in the upper half of its extent, prismatic and flattened below, and has three borders and three surfaces.- Anterior :... |
| Clavicular part of pectoralis major Pectoralis major muscle The pectoralis major is a thick, fan-shaped muscle, situated at the chest of the body. It makes up the bulk of the chest muscles in the male and lies under the breast in the female... |
Clavicle | Lateral lip of bicipital groove of humerus | |
| Long head of biceps brachii | Supraglenoid tubercle Supraglenoid tubercle The supraglenoid tubercle is a region of the scapula to which the long head of the biceps brachii muscle attaches. It is a small, rough projection just superior to the Glenoid cavity near the base of the coracoid process... of scapula Scapula In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle .... |
Tuberosity of radius Radial tuberosity Beneath the neck of the radius, on the medial side, is an eminence, the radial tuberosity; its surface is divided into:* a posterior, rough portion, for the insertion of the tendon of the biceps brachii.... , Deep fascia of forearm Antebrachial fascia The antebrachial fascia continuous above with the brachial fascia, is a dense, membranous investment, which forms a general sheath for the muscles in this region; it is attached, behind, to the olecranon and dorsal border of the ulna, and gives off from its deep surface numerous intermuscular... |
|
| Short head of biceps brachii | Coracoid process of scapula Scapula In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle .... |
||
| Coracobrachialis Coracobrachialis muscle The Coracobrachialis is the smallest of the three muscles that attach to the coracoid process of the scapula. It is situated at the upper and medial part of the arm.... |
Coracoid process | Medial aspect of shaft of humerus | |
| Extension Extension (kinesiology) In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of... (40°) |
Posterior fibers of deltoid | Spine of scapula Spine of scapula The spine of the scapula is a prominent plate of bone, which crosses obliquely the medial four-fifths of the scapula at its upper part, and separates the supra- from the infraspinatous fossa.... |
Middle of lateral surface of shaft of humerus |
| Latissimus dorsi Latissimus dorsi muscle The latissimus dorsi , meaning 'broadest muscle of the back' , is the larger, flat, dorso-lateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region.The latissimus dorsi is responsible for extension,... |
Iliac crest Iliac crest -External links: - "Superficial muscles of the gluteal region and posterior thigh." - "Anterior Abdominal Wall: Osteology and Surface Anatomy " - "The Back, Posterior View" * *... , lumbar fascia Lumbar fascia -Function:In addition to the usual function of fasciae, the lumbar fascia is an attachment for the gluteus maximus muscle and the latissimus dorsi muscle.... , spines of lower six thoracic vertebrae Thoracic vertebrae In human anatomy, twelve thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper... , lower 3–4 rib Rib In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax... s, inferior angle of scapula Inferior angle of the scapula The inferior angle of the scapula , thick and rough, is formed by the union of the vertebral and axillary borders; its dorsal surface affords attachment to the Teres major and frequently to a few fibers of the Latissimus dorsi.... |
Floor of bicipital groove of humerus | |
| Teres major Teres major muscle The teres major muscle is a muscle of the upper limb and one of six scapulohumeral muscles. It is a thick but somewhat flattened muscle, innervated by the lower subscapular nerve .-Origin and insertion:... |
Lateral border of scapula Lateral border of the scapula The lateral border is the thickest of the three borders of the scapula.It begins above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle.... |
Medial lip of bicipital groove of humerus | |
| Abduction Abduction (kinesiology) Abduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:* of arm at shoulder ** Supraspinatus** Deltoid* of hand at wrist... (160°–180°) |
Middle fibers of deltoid | Acromion process of scapula | Middle of lateral surface of shaft of humerus |
| Supraspinatus Supraspinatus muscle The supraspinatus is a relatively small muscle of the upper arm that runs from the supraspinatous fossa superior of the scapula to the greater tubercle of the humerus. It is one of the four rotator cuff muscles and also abducts the arm at the shoulder... |
Supraspinous fossa of scapula | Greater tuberosity Greater tubercle The greater tubercle of the humerus is situated lateral to the head of the humerus and posteriolateral to the lesser tubercle.Its upper surface is rounded and marked by three flat impressions.... of humerus |
|
| Adduction Adduction Adduction is a movement which brings a part of the anatomy closer to the middle sagittal plane of the body. It is opposed to abduction.-Upper limb:* of arm at shoulder ** Subscapularis** Teres major** Pectoralis major** Infraspinatus... (30°–40°) |
Sternal part of pectoralis major | Sternum, upper six costal cartilages | Lateral lip of bicipital groove of humerus |
| Latissimus dorsi | Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3-4 ribs, inferior angle of scapula | Floor of bicipital groove of humerus | |
| Teres major Teres major muscle The teres major muscle is a muscle of the upper limb and one of six scapulohumeral muscles. It is a thick but somewhat flattened muscle, innervated by the lower subscapular nerve .-Origin and insertion:... |
Lower third of lateral border of scapula Lateral border of the scapula The lateral border is the thickest of the three borders of the scapula.It begins above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle.... |
Medial lip of bicipital groove of humerus | |
| Teres minor Teres minor muscle The teres minor is a narrow, elongated muscle of the rotator cuff.-Origin:It arises from the dorsal surface of the axillary border of the scapula for the upper two-thirds of its extent, and from two aponeurotic laminæ, one of which separates it from the infraspinatus muscle, the other from the... |
Upper two thirds of lateral border of scapula | Greater tuberosity of humerus | |
| Lateral rotation External rotation External rotation is rotation away from the center of the body.The muscles of external rotation include:* of arm/humerus at shoulder** Deltoid muscle** Infraspinatus** Teres minor* of thigh/femur at hip ** Gluteus maximus... ( ) |
Infraspinatus Infraspinatus muscle In human anatomy, the infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa. As one of the four muscles of the rotator cuff, the main function of the infraspinatus is to externally rotate the arm and stabilize the shoulder joint.-Origin and... |
Infraspinous fossa of scapula | Greater tuberosity of humerus |
| Teres minor | Upper two thirds of lateral border of scapula | Greater tuberosity of humerus | |
| Posterior fibers of deltoid | Spine of scapula | Middle of lateral surface of shaft of humerus | |
| Medial rotation Internal rotation In anatomy, internal rotation is rotation towards the center of the body.The muscles of internal rotation include:* of arm/humerus at shoulder** Deltoid muscle** Subscapularis** Teres major** Latissimus dorsi... ( ) |
Subscapularis Subscapularis muscle The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint.-Origin and insertion:... |
Subscapular fossa Subscapular fossa The costal or ventral surface of the scapula presents a broad concavity, the subscapular fossa.It provides an attachment for the subscapularis muscle.-External links: - "Scapular Region: Scapula "... |
Lesser tuberosity Lesser tubercle The lesser tubercle of the humerus, although smaller, is more prominent than the greater tubercle: it is situated in front, and is directed medially and anteriorly.... of humerus |
| Latissimus dorsi | Iliac crest, lumbar fascia, spines of lower 3-4 ribs, inferior angle of scapula | Floor of bicipital groove of humerus | |
| Teres major | Lower third of lateral border of scapula | Medial lip of bicipital groove of humerus | |
| Anterior fibers of deltoid | Clavicle | Middle of lateral surface of shaft of humerus |
Capsule
The glenohumeral joint has a loose capsuleJoint capsule
An articular capsule is an envelope surrounding a synovial joint.-Layers:Each capsule consists of two layers:* an outer layer composed of avascular white fibrous tissue...
that is lax inferiorly and therefore is at risk of dislocation
Dislocation (medicine)
Joint dislocation, or luxation , occurs when bones in a joint become displaced or misaligned. It is often caused by a sudden impact to the joint. The ligaments always become damaged as a result of a dislocation...
inferiorly. The long head of the biceps brachii muscle
Biceps brachii muscle
In human anatomy, the biceps brachii, or simply biceps in common parlance, is, as the name implies, a two-headed muscle located on the upper arm. Both heads arise on the scapula and join to form a single muscle belly which is attached to the upper forearm...
travels inside the capsule to attach to the supraglenoid tubercle
Supraglenoid tubercle
The supraglenoid tubercle is a region of the scapula to which the long head of the biceps brachii muscle attaches. It is a small, rough projection just superior to the Glenoid cavity near the base of the coracoid process...
of the scapula.
Because the tendon is inside the capsule, it requires a synovial tendon sheath to minimize friction.
A number of bursae
Bursa (anatomy)
A bursa is a small fluid-filled sac lined by synovial membrane with an inner capillary layer of slimy fluid . It provides a cushion between bones and tendons and/or muscles around a joint. This helps to reduce friction between the bones and allows free movement...
in the capsule aid mobility. Namely, they are the subdeltoid bursa (between the joint capsule and deltoid muscle), subcoracoid bursa (between joint capsule and coracoid process of scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
), coracobrachial bursa (between subscapularis muscle and tendon of coracobrachialis muscle), subacromial bursa (between joint capsule and acromion of scapula) and the subscapular bursa (between joint capsule and tendon of subscapularis muscle
Subscapularis muscle
The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint.-Origin and insertion:...
, also known as subtendinous bursa of subscapularis muscle). The bursa are formed by the synovial membrane of the joint capsule. An inferior pouching of the joint capsule between teres minor and subscapularis is known as the axillary recess.
The shoulder joint is a muscle dependent joint as it lacks strong ligaments.
Ligaments
- Superior, middle and inferior glenohumeral ligamentsGlenohumeral ligamentsIn human anatomy, the glenohumeral ligaments are three ligaments on the anterior side of the glenohumeral joint...
- Coracohumeral ligamentCoracohumeral ligamentThe coracohumeral ligament is a broad ligament which strengthens the upper part of the capsule of the shoulder joint.It arises from the lateral border of the coracoid process, and passes obliquely downward and lateralward to the front of the greater tubercle of the humerus, blending with the tendon...
- Transverse humeral ligamentTransverse humeral ligamentThe transverse humeral ligament is a broad band passing from the lesser to the greater tubercle of the humerus, and always limited to that portion of the bone which lies above the epiphysial line....
Pathology
The capsule can become inflamed and stiff, with abnormal bands of tissue (adhesionsAdhesion (medicine)
Adhesions are fibrous bands that form between tissues and organs, often as a result of injury during surgery. They may be thought of as internal scar tissue that connect tissues not normally connected.-Pathophysiology:...
) growing between the joint surfaces, causing pain and restricting movement of the shoulder, a condition known as frozen shoulder
Frozen shoulder
Frozen shoulder, medically referred to as adhesive capsulitis, is a disorder in which the shoulder capsule, the connective tissue surrounding the glenohumeral joint of the shoulder, becomes inflamed and stiff, greatly restricting motion and causing chronic pain.Adhesive capsulitis is a painful and...
or adhesive capsulitis.
Acromion
The acromion ranks among the osseous structures which feature the highest variability. The lateral margin could have a smooth convex arch, but also present several knobs, spikes, sharp or diffuse fissures, or even a large flat depression. Those shape variations have no functional significance compared to the variations at the anterior third, which essentially affect the subacromial space for the rotator cuff.Bigliani proclaimed 3 types:
- Type 1: flattened
- Type 2: curved
- Type 3: hooked
Labrum
The glenoid labrum is a wedge shaped fibro-cartilaginous structure that is fixed at the glenoid border of the scapula and surrounds the glenoid like a wreath. The labrum doubles the joint surface of the glenoid for the humeral head and is also responsible for a certain stability in the antero-posterior movements. The following variants from the norm can be mis-interpreted as so-called SLAP lesions.The transversal stratification from the lower edge of the acromion up to the lower edge of the glenoid fossa is mandatory in order to depict changes of the glenoid labrum. Furthermore are oblique coronal or oblique sagittal planes not necessary examinations. Yet can they help to depict precisely the rotator cuff or the shape of the humeral head.
1. The sublabral superior recess:
Linear inflow of contrast agent between labrum and glenoid at the paracoronal sequence. Typically straightened medially towards the tuberculum supraglenoidale. The superior labrum often isn’t completely attached to the glenoid. There can be a variously deep sulcus which communicates with the joint cavity.
This anatomical variation is depictable at the 12 o’clock position in the oblique sagittal MR projection and can be subdivided into 3 types.
- Type 1: The labral bicipital complex is entirely fixed at the glenoid rim, that’s why the glenoid cannot be distinguished arthroscopically from the labrum.
- Type 2: A narrow sulcus between the labrum and the glenoid rim.
- Type 3: An extended sulcus between the labrum and the glenoid rim, which allows now an arthroscopic distinction between labrum and glenoidal cartilage.
Park et al. examined 95 asymptomatic shoulders using MRA and was able to demonstrate a recess in 30% of the cases.
2. The sublabral foramen:
It can be found in around 11% of the cases and should not be confused with a sublabral superior recess. The range of the foramen is large. From only few millimeters up to a complete ablation of the antero-superior labrum. In contrast to the sublabral superior recess, is the sublabral superior foramen depictable in the oblique sagittal projection, positioned antero-superiorly at around 2 o’clock. And Inflow of contrast agent can be seen at the axial sequence between labrum and glenoid. It can sometimes be found combined with a sublabral superior recess. Enhanced MR imaging via an intraarticular contrast agent injection, can lead to a false positive interpretation as a labral injury. This variation of the norm is positioned antero-superiorly. Bankart lesions for example have an antero-inferior localisation.
3. The Buford complex:
The Buford complex can be found in 1.5% of the population. It consists of a ribbon-like thickening of the medial gleno-humeral ligament (GHL) and is further characterized by a lack of anterior superior labrum. The medial GHL inserts just at the area of the antero-superior glenoid. A thickened medial GHL can be confused with a displaced labral fragment on the arthroscope.
And furthermore:
4. In 50% of the cases a triangular linear signal increasement can be found at the area of the anterior labrum through hyaline cartilage. This is the most common shape and accounts for 73% in the posterior area and for 45% in the anterior area.
5. In 20% of the cases the labrum is rounded.
6. In 7% of the cases the labrum is comma-shaped flattened.
7. In 15% of the cases the labrum is splitted.
8. In 8% of the cases the labrum is notched.
9. The labrum has a central signal increasement.
10. The labrum has a linear signal increasement.
Anterior capsule
There are four known anatomical variants of the anterior capsule and ligaments in the anterior region.- 1: The classical type with three ligaments.
- 2: A ribbon-like representation of the medial gleno-humeral ligament and a normal inferior GHL.
- 3: A confluence of the medial and inferior GHL.
- 4: The complete lack of gleno-humeral ligaments.
Biceps tendon insertion into the labrum
The complex composed of glenoid, labrum and gleno-humeral ligaments is essential for the shoulder stability. The glenoid labrum is not a morphological entity. It consists of different zones and features multiple anatomical variants. These are of special importance at the areas superior and antero-superior of the long biceps tendon insertion. A clear discrimination between physiological varieties and pathological findings is of great clinical significance. Not via imaging, but on corpses defined Barthel T. et al. anatomical structures of the glenoid labrum. The labrum is at the postero-inferior parts firmly adhered to the glenoid. However, the supero-anterior part is rather loose and can be subdivided into a cranial labrum-biceps-tendon complex and an anterior labrum-capsule-complex.The fibers of the long biceps tendon irradiate in different forms into the labrum. Subdivided into an anterior and a posterior rein. After Vangsness et al. there are 4 types, of which type 2 is the most common.
See also
- Shoulder girdle (Pectoral girdle)
- ShoulderShoulderThe human shoulder is made up of three bones: the clavicle , the scapula , and the humerus as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which...
- Acromioclavicular jointAcromioclavicular jointThe acromioclavicular joint, or AC joint, is a joint at the top of the shoulder. It is the junction between the acromion and the clavicle. -Function:...
- Sternoclavicular joint