In anatomy, the scapula (plural scapulae or scapulas), also known as shoulder bone, shoulder blade, wing bone or blade bone, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones the scapulae are paired, with the scapula on either side of the body being roughly a mirror image of the other. The name derives from early Roman times when it was thought that the bone resembled a trowel or small shovel.
In compound terms, the prefix omo- is used for the shoulder blade in Latin medical terminology. The prefix is derived from ὦμος (ōmos), the Ancient Greek word for shoulder, and is cognate with the Latin (h)umerus.
The upper picture is an anterior (from the front) view of the thorax and shoulder girdle. The lower picture is a posterior (from the rear) view of the thorax (scapula shown in red.)
|Anatomical terms of bone|
The scapula is a wide, flat bone lying on the thoracic wall that provides an attachment for three groups of muscles: intrinsic, extrinsic, and stabilising and rotating muscles. The intrinsic muscles of the scapula include the muscles of the rotator cuff—the subscapularis, teres minor, supraspinatus, and infraspinatus. These muscles attach to the surface of the scapula and are responsible for the internal and external rotation of the shoulder joint, along with humeral abduction.
The extrinsic muscles include the biceps, triceps, and deltoid muscles and attach to the coracoid process and supraglenoid tubercle of the scapula, infraglenoid tubercle of the scapula, and spine of the scapula. These muscles are responsible for several actions of the glenohumeral joint.
The third group, which is mainly responsible for stabilization and rotation of the scapula, consists of the trapezius, serratus anterior, levator scapulae, and rhomboid muscles. These attach to the medial, superior, and inferior borders of the scapula.
The head, processes, and the thickened parts of the bone contain cancellous tissue; the rest consists of a thin layer of compact tissue.
The central part of the supraspinatus fossa and the upper part of the infraspinatous fossa, but especially the former, are usually so thin in humans as to be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent muscles are separated only by fibrous tissue. The scapula has two surfaces, three borders, three angles, and three processes.
The front of the scapula (also known as the costal or ventral surface) has a broad concavity called the subscapular fossa, to which the subscapularis muscle attaches. The medial two-thirds of the fossa have 3 longitudinal oblique ridges, and another thick ridge adjoins the lateral border; they run outward and upward. The ridges give attachment to the tendinous insertions, and the surfaces between them to the fleshy fibers, of the subscapularis muscle. The lateral third of the fossa is smooth and covered by the fibers of this muscle.
At the upper part of the fossa is a transverse depression, where the bone appears to be bent on itself along a line at right angles to and passing through the center of the glenoid cavity, forming a considerable angle, called the subscapular angle; this gives greater strength to the body of the bone by its arched form, while the summit of the arch serves to support the spine and acromion.
The costal surface superior of the scapula is the origin of 1st digitation for the serratus anterior origin.
The back of the scapula (also called the dorsal or posterior surface) is arched from above downward, and is subdivided into two unequal parts by the spine of the scapula. The portion above the spine is called the supraspinous fossa, and that below it the infraspinous fossa. The two fossae are connected by the spinoglenoid notch, situated lateral to the root of the spine.
There is a ridge on the outer part of the back of the scapula. This runs from the lower part of the glenoid cavity, downward and backward to the vertebral border, about 2.5 cm above the inferior angle. Attached to the ridge is a fibrous septum, which separates the infraspinatus muscle from the Teres major and Teres minor muscles. The upper two-thirds of the surface between the ridge and the axillary border is narrow, and is crossed near its center by a groove for the scapular circumflex vessels; the Teres minor attaches here.
The broad and narrow portions above alluded to are separated by an oblique line, which runs from the axillary border, downward and backward, to meet the elevated ridge: to it is attached a fibrous septum which separates the Teres muscles from each other.
Its lower third presents a broader, somewhat triangular surface, the inferior angle of the scapula, which gives origin to the Teres major, and over which the Latissimus dorsi glides; frequently the latter muscle takes origin by a few fibers from this part.
The acromion forms the summit of the shoulder, and is a large, somewhat triangular or oblong process, flattened from behind forward, projecting at first laterally, and then curving forward and upward, so as to overhang the glenoid cavity.
There are 3 angles:
The superior angle of the scapula or medial angle, is covered by the trapezius muscle. This angle is formed by the junction of the superior and medial borders of the scapula. The superior angle is located at the approximate level of the second thoracic vertebra. The superior angle of the scapula is thin, smooth, rounded, and inclined somewhat lateralward, and gives attachment to a few fibers of the levator scapulae muscle.
The inferior angle of the scapula is the lowest part of the scapula and is covered by the latissimus dorsi muscle. It moves forwards round the chest when the arm is abducted. The inferior angle is formed by the union of the medial and lateral borders of the scapula. It is thick and rough and its posterior or back surface affords attachment to the teres major and often to a few fibers of the latissimus dorsi. The anatomical plane that passes vertically through the inferior angle is named the scapular line.
The lateral angle of the scapula or glenoid angle also known as the head of the scapula is the thickest part of the scapula. It is broad and bears the glenoid cavity on its articular surface which is directed forward, laterally and slightly upwards, and articulates with the head of the humerus. The inferior angle is broader below than above and its vertical diameter is the longest. The surface is covered with cartilage in the fresh state; and its margins, slightly raised, give attachment to a fibrocartilaginous structure, the glenoidal labrum, which deepens the cavity. At its apex is a slight elevation, the supraglenoid tuberosity, to which the long head of the biceps brachii is attached.
The neck of the scapula is the slightly constricted portion which surrounds the head and is more distinct below and behind than above and in front.
There are three borders of the scapula:
The scapula is ossified from 7 or more centers: one for the body, two for the coracoid process, two for the acromion, one for the vertebral border, and one for the inferior angle. Ossification of the body begins about the second month of fetal life, by an irregular quadrilateral plate of bone forming, immediately behind the glenoid cavity. This plate extends to form the chief part of the bone, the scapular spine growing up from its dorsal surface about the third month. Ossification starts as membranous ossification before birth. After birth, the cartilaginous components would undergo endochondral ossification. The larger part of the scapula undergoes membranous ossification. Some of the outer parts of the scapula are cartilaginous at birth, and would therefore undergo endochondral ossification.
At birth, a large part of the scapula is osseous, but the glenoid cavity, the coracoid process, the acromion, the vertebral border and the inferior angle are cartilaginous. From the 15th to the 18th month after birth, ossification takes place in the middle of the coracoid process, which as a rule becomes joined with the rest of the bone about the 15th year.
Between the 14th and 20th years, the remaining parts ossify in quick succession, and usually in the following order: first, in the root of the coracoid process, in the form of a broad scale; secondly, near the base of the acromion; thirdly, in the inferior angle and contiguous part of the vertebral border; fourthly, near the outer end of the acromion; fifthly, in the vertebral border. The base of the acromion is formed by an extension from the spine; the two nuclei of the acromion unite, and then join with the extension from the spine. The upper third of the glenoid cavity is ossified from a separate center (sub coracoid), which appears between the 10th and 11th years and joins between the 16th and the 18th years. Further, an epiphysial plate appears for the lower part of the glenoid cavity, and the tip of the coracoid process frequently has a separate nucleus. These various epiphyses are joined to the bone by the 25th year.
Failure of bony union between the acromion and spine sometimes occurs (see os acromiale), the junction being effected by fibrous tissue, or by an imperfect articulation; in some cases of supposed fracture of the acromion with ligamentous union, it is probable that the detached segment was never united to the rest of the bone.
"In terms of comparative anatomy the human scapula represents two bones that have become fused together; the (dorsal) scapula proper and the (ventral) coracoid. The epiphyseal line across the glenoid cavity is the line of fusion. They are the counterparts of the ilium and ischium of the pelvic girdle."— R. J. Last – 'Last's Anatomy
The following muscles attach to the scapula:
|Pectoralis Minor||insertion||coracoid process|
|Serratus Anterior||insertion||medial border|
|Triceps Brachii (long head)||origin||infraglenoid tubercle|
|Biceps Brachii (short head)||origin||coracoid process|
|Biceps Brachii (long head)||origin||supraglenoid tubercle|
|Rhomboid Major||insertion||medial border|
|Rhomboid Minor||insertion||medial border|
|Levator Scapulae||insertion||medial border|
|Trapezius||insertion||spine of scapula|
|Deltoid||origin||spine of scapula|
|Teres Minor||origin||lateral border|
|Teres Major||origin||lateral border|
|Latissimus Dorsi (a few fibers, attachment may be absent)||origin||inferior angle|
Movements of the scapula are brought about by the scapular muscles. The scapula can perform six actions:
Because of its sturdy structure and protected location, fractures of the scapula are uncommon. When they do occur, they are an indication that severe chest trauma has occurred. Scapular fractures involving the neck of the scapula have two patterns. One (rare) type of fracture is through the anatomical neck of the scapula. The other more common type of fracture is through the surgical neck of the scapula. The surgical neck exits medial to the coracoid process.
An abnormally protruding inferior angle of the scapula is known as a winged scapula and can be caused by paralysis of the serratus anterior muscle. In this condition the sides of the scapula nearest the spine are positioned outward and backward. The appearance of the upper back is said to be wing-like. In addition, any condition causing weakness of the serratus anterior muscle may cause scapular "winging".
The scapula plays an important role in shoulder impingement syndrome.
Abnormal scapular function is called scapular dyskinesis. One action the scapula performs during a throwing or serving motion is elevation of the acromion process in order to avoid impingement of the rotator cuff tendons. If the scapula fails to properly elevate the acromion, impingement may occur during the cocking and acceleration phase of an overhead activity. The two muscles most commonly inhibited during this first part of an overhead motion are the serratus anterior and the lower trapezius. These two muscles act as a force couple within the glenohumeral joint to properly elevate the acromion process, and if a muscle imbalance exists, shoulder impingement may develop.
The name scapula as synonym of shoulder blade is of Latin origin. It is commonly used in medical English and is part of the current official Latin nomenclature, Terminologia Anatomica.
In classical Latin scapula is only used in its plural scapulae. Although some sources mention that scapulae is used to refer during Roman antiquity to the shoulders  or to the shoulder blades, others persist in that the Romans used scapulae only to refer to the back, in contrast to the pectus, the Latin name for breast  or chest.
The Roman encyclopedist Aulus Cornelius Celsus who lived during the beginning of the era, also used scapulae to refer to the back. He used os latum scapularum to refer to the shoulder blade. This expressions can be translated as broad (Latin: latum) bone (Latin: os) of the back (Latin: scapularum).
A similar expression in ancient Greek can be seen in the writings of the Greek philosopher Aristoteles and in the writings of the Greek physician Galen. They both use the name ὠμοπλάτη to refer to the shoulder blade. This compound consists of ancient Greek ὦμος, shoulder  and πλάτη, blade  or flat or broad object. Πλάτη in its plural πλάται without ὦμο- was also used in ancient Greek to refer to the shoulder blades. In anatomic Latin, ὠμοπλάτη is Latinized as omoplata.
The Latin word umerus is related to ὦμος. The Romans referred with umerus to what is now commonly known in English as the following 3 bones: humerus or the upper bone of the arm, the clavicle or the collarbone and the scapula or the shoulder blade. The spelling humerus is actually incorrect in classical Latin.
Those three bones were referred to as the ossa (Latin: bones) umeri (Latin: of the umerus). Umerus was also used to refer specifically to the shoulder. This mirrors the use of ὦμος in ancient Greek as that could refer to the shoulder with the upper arm  or to the shoulder  alone.
Since Celsus, the os umeri could refer specifically to the upper bone of the arm. The 16th century anatomist Andreas Vesalius used humerus to refer to the clavicle. Besides the aforementioned os latum scapularum, Celsus used os latum umeri to refer to the shoulder blade. Similarly, Laurentius used the expression latitudo umeri (Latitudo = breadth, width ) to refer to the shoulder blade.
The Roman physician Caelius Aurelianus (5th century) used pala to refer to the shoulder blade. The name pala is normally used to refer to a spade in Latin and was therefore probably used by Caelius Aurelianus to describe the shoulder blade, as both exhibit a flat curvature.
During the Middle Ages spathula was used to refer to the shoulder blade. Spathula is a diminutive of spatha, with the latter originally meaning broad, two-edged sword without a point, broad, flat, wooden instrument for stirring any liquid, a spattle, spatula  or spathe of the palm tree  and its diminutive used in classical and late Latin for referring to a leg of pork  or a little palmbranch.
The English word spatula is actually derived from Latin spatula, an orthographic variant of spathula. Oddly enough, classical Latin non-diminutive spatha can be translated as English spatula, while its Latin diminutive spatula is not translated as English spatula.
Latin spatha is derived from ancient Greek σπάθη. Therefore, the form spathula is more akin to its origin than spatula. Ancient Greek σπάθη has a similar meaning as Latin spatha, as any broad blade, and can also refer to a spatula or to the broad blade of a sword., but also to the blade of an oar. The aforementioned πλάται for shoulder blades was also used for blades of an oar. Concordantly σπάθη was also used to refer to the shoulder blade.
The English word spade, as well as the Dutch equivalent spade  is cognate with σπάθη. Please notice, that the aforementioned term pala as applied by Roman physician Caelius Aurelianus, also means spade. Pala is probably related to the Latin verb pandere, to spread out, and to extend. This verb is thought to be derived from an earlier form spandere, with the root spa-. Σπάθη is actually derived from the similar root spē(i), that means to extend.
It seems that os latum scapularum, ὠμοπλάτη, πλάται, pala, spathula and σπάθη all refer to the same aspect of the shoulder blade, i.e. being a flat, broad blade, with the latter three words etymological related to each other.
After the Middle Ages, the name scapula for shoulder blade became dominant. The word scapula can etymologically be explained by its relatedness to ancient Greek verb σκάπτειν, to dig. This relatedness give rise to several possible explanations.
First, the noun σκάπετος, trench  derived from this verb, and the to scapula related noun σκαφη, similarly derived from the aforementioned verb, might connect scapula to the notion of (con)cavity. The name scapula might be related that due to existence of the spine of the scapula a concavity exist in the scapula. Otherwise, the designation scapulae is also seen as synonym of ancient Greek συνωμία, the space between the shoulder blades, that is obviously concave. Συνωμία consists of σύν, together with, and ὦμος, shoulder.
Second, scapula, due to its relatedness to σκάπτειν might originally meant shovel. Similarly to the resemblance between the Latin pala (spade) and the shoulder blade, a resemblance might be felt between the shape of a shovel and the shoulder blade. Alternatively, the shoulder blade might be used originally for digging and shoveling.
Shoulder blade is colloquial name for this bone. Shoulder is cognate to German and Dutch equivalents Schulter and schouder. There are a few etymological explanations for shoulder. The first supposes that shoulder can be literally translated as that which shields or protects, as its possibly related to Icelandic skioldr, shield and skyla, to cover, to defend. The second explanation relates shoulder to ancient Greek σκέλος, leg. The latter spots the possible root skel-, meaning to bend, to curve. The third explanation links the root skel- to to cleave. This meaning could refer to the shape of the shoulder blade.
In fish, the scapular blade is a structure attached to the upper surface of the articulation of the pectoral fin, and is accompanied by a similar coracoid plate on the lower surface. Although sturdy in cartilagenous fish, both plates are generally small in most other fish, and may be partially cartilagenous, or consist of multiple bony elements.
In the early tetrapods, these two structures respectively became the scapula and a bone referred to as the procoracoid (commonly called simply the "coracoid", but not homologous with the mammalian structure of that name). In amphibians and reptiles (birds included), these two bones are distinct, but together form a single structure bearing many of the muscle attachments for the forelimb. In such animals, the scapula is usually a relatively simple plate, lacking the projections and spine that it possesses in mammals. However, the detailed structure of these bones varies considerably in living groups. For example, in frogs, the procoracoid bones may be braced together at the animal's underside to absorb the shock of landing, while in turtles, the combined structure forms a Y-shape in order to allow the scapula to retain a connection to the clavicle (which is part of the shell). In birds, the procoracoids help to brace the wing against the top of the sternum.
In the fossil therapsids, a third bone, the true coracoid, formed just behind the procoracoid. The resulting three-boned structure is still seen in modern monotremes, but in all other living mammals, the procoracoid has disappeared, and the coracoid bone has fused with the scapula, to become the coracoid process. These changes are associated with the upright gait of mammals, compared with the more sprawling limb arrangement of reptiles and amphibians; the muscles formerly attached to the procoracoid are no longer required. The altered musculature is also responsible for the alteration in the shape of the rest of the scapula; the forward margin of the original bone became the spine and acromion, from which the main shelf of the shoulder blade arises as a new structure.
In dinosaurs the main bones of the pectoral girdle were the scapula (shoulder blade) and the coracoid, both of which directly articulated with the clavicle. The clavicle was present in saurischian dinosaurs but largely absent in ornithischian dinosaurs. The place on the scapula where it articulated with the humerus (upper bone of the forelimb) is the called the glenoid. The scapula serves as the attachment site for a dinosaur's back and forelimb muscles.
In human anatomy, the acromion (from Greek: akros, "highest", ōmos, "shoulder", plural: acromia) is a bony process on the scapula (shoulder blade). Together with the coracoid process it extends laterally over the shoulder joint. The acromion is a continuation of the scapular spine, and hooks over anteriorly. It articulates with the clavicle (collar bone) to form the acromioclavicular joint.Cat anatomy
The anatomy of the domestic cat is similar to that of other members of the genus Felis.Clavicle
The clavicle or collarbone is a long bone that serves as a strut between the shoulder blade and the sternum or breastbone. There are two clavicles, one on the left and one on the right. The clavicle is the only long bone in the body that lies horizontally. Together with the shoulder blade it makes up the shoulder girdle. It is a touchable bone and in people who have less fat in this region, the location of the bone is clearly visible, as it creates a bulge in the skin. It receives its name from the Latin: clavicula ("little key") because the bone rotates along its axis like a key when the shoulder is abducted. The clavicle is the most commonly fractured bone. It can easily be fractured due to impacts to the shoulder from the force of falling on outstretched arms or by a direct hit.Coracoid
A coracoid is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (which is to say marsupials and placentals). In therian mammals (including humans), a coracoid process is present as part of the scapula, but this is not homologous with the coracoid bone of most other animals.In other tetrapods it joins the scapula to the front end of the sternum and has a notch on the dorsal surface which, along with a similar notch on the ventral surface of the scapula, forms the socket in which the proximal end of the humerus (upper arm bone) is located. The acrocoracoid process is an expansion adjacent to this contact surface, to which the shoulderward end of the biceps brachii muscle attaches in these animals. In birds (and generally theropods and related animals), the entire unit is rigid and called scapulocoracoid. This plays a major role in bird flight. In dinosaurs the main bones of the pectoral girdle were the scapula (shoulder blade) and the coracoid, both of which directly articulated with the clavicle.In fish it provides the base for the pectoral fin.Monotremes, as well as the extinct therapsids, possess both the coracoid bone of reptiles (here referred to as the procoracoid, or anterior coracoid), and the coracoid process of other mammals, with the latter being present as a separate bone.Coracoid process
The coracoid process (from Greek κόραξ, raven) is a small hook-like structure on the lateral edge of the superior anterior portion of the scapula (hence: coracoid, or "like a raven's beak"). Pointing laterally forward, it, together with the acromion, serves to stabilize the shoulder joint. It is palpable in the deltopectoral groove between the deltoid and pectoralis major muscles.Glenoid cavity
The glenoid cavity or glenoid fossa of scapula is a part of the shoulder. It 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 glenohumeral joint along with the humerus. This type of joint is classified as a synovial, ball and socket joint. The humerus is held in place within the glenoid cavity by means of the long head of the biceps tendon. This tendon originates on the superior margin of the glenoid cavity and loops over the shoulder, bracing humerus against the cavity. The rotator cuff also reinforces this joint more specifically with the supraspinatus tendon to hold the head of the humerus in the glenoid cavity.
The cavity surface is covered with cartilage in the fresh state, and its margins, slightly raised, give attachment to a fibrocartilaginous structure, the glenoid labrum, which deepens the cavity. This cartilage is very susceptible to tearing. When torn, it is most commonly known as a SLAP lesion which is generally caused by repetitive shoulder movements.
Compared to the acetabulum (at the hip-joint) the glenoid cavity is relatively shallow. This makes the shoulder joint prone to dislocation (luxation). Strong glenohumeral ligaments and muscles prevents dislocation in most cases.
By being so shallow the glenoid cavity allows the shoulder joint to have the greatest mobility of all joints in the body, allowing 120 degrees of unassisted flexion. Additional range of motion in shoulder flexion (typically up to 180 degrees in humans) is also accomplished by the great mobility of the scapula (shoulder blade) through a process known as scapulohumeral rhythm.Glenoid labrum
The glenoid labrum (glenoid ligament) is a fibrocartilaginous structure (not a fibrocartilage as previously thought) rim attached around the margin of the glenoid cavity in the shoulder blade. The shoulder joint is considered a ball and socket joint. However, in bony terms the 'socket' (the glenoid fossa of the scapula) is quite shallow and small, covering at most only a third of the 'ball' (the head of the humerus). The socket is deepened by the glenoid labrum.
The labrum is triangular in section; the base is fixed to the circumference of the cavity, while the free edge is thin and sharp.
It is continuous above with the tendon of the long head of the biceps brachii, which gives off two fascicles to blend with the fibrous tissue of the labrum.Humerus
The humerus (, plural: humeri) is a long bone that runs through the thigh of the arm (also known as the Tharm). It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes (tubercles, sometimes called tuberosities). The body is cylindrical in its upper portion, and more prismatic below. The lower extremity consists of 2 epicondyles, 2 processes (trochlea & capitulum), and 3 fossae (radial fossa, coronoid fossa, and olecranon fossa). As well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons.Inferior transverse ligament of scapula
The inferior transverse ligament (spinoglenoid ligament) is a weak membranous band, situated behind the neck of the scapula and stretching from the lateral border of the spine to the margin of the glenoid cavity.
It forms an arch under which the transverse scapular vessels and suprascapular nerve enter the infraspinatous fossa.Infraglenoid tubercle
The infraglenoid tubercle is the part of the scapula from which the long head of the triceps brachii originates.
The infraglenoid tubercle is a tubercle located on the lateral part of the scapula, inferior to (below) the glenoid cavity. The name infraglenoid tubercle refers to its location below the glenoid cavity.Scapular fracture
A scapular fracture is a fracture of the scapula, the shoulder blade. The scapula is sturdy and located in a protected place, so it rarely breaks. When it does, it is an indication that the individual was subjected to a considerable amount of force and that severe chest trauma may be present. High-speed vehicle accidents are the most common cause. This could be anywhere from a car accident, motorcycle crash, or high speed bicycle crash but falls and blows to the area can also be responsible for the injury. Signs and symptoms are similar to those of other fractures: they include pain, tenderness, and reduced motion of the affected area although symptoms can take a couple of days to appear. Imaging techniques such as X-ray are used to diagnose scapular fracture, but the injury may not be noticed in part because it is so frequently accompanied by other, severe injuries that demand attention. The injuries that usually accompany scapular fracture generally have the greatest impact on the patient's outcome. However, the injury can also occur by itself; when it does, it does not present a significant threat to life. Treatment involves pain control and immobilizing the affected area, and, later, physical therapy.Shoulder
The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The shoulder joint, also known as the glenohumeral joint, is the major joint of the shoulder, but can more broadly include the acromioclavicular joint. In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula, and the head sits in the glenoid cavity. The shoulder is the group of structures in the region of the joint.The shoulder joint is the main joint of the shoulder. It is a ball and socket joint that allows the arm to rotate in a circular fashion or to hinge out and up away from the body. The joint capsule is a soft tissue envelope that encircles the glenohumeral joint and attaches to the scapula, humerus, and head of the biceps. It is lined by a thin, smooth synovial membrane. The rotator cuff is a group of four muscles that surround the shoulder joint and contribute to the shoulder's stability. The muscles of the rotator cuff are supraspinatus, subscapularis, infraspinatus, and teres minor. The cuff adheres to the glenohumeral capsule and attaches to the humeral head.
The shoulder must be mobile enough for the wide range actions of the arms and hands, but stable enough to allow for actions such as lifting, pushing, and pulling.Shoulder girdle
The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of the clavicle, scapula, and coracoid. Some mammalian species (such as the dog and the horse) have only the scapula.
The pectoral girdles are to the upper limbs as the pelvic girdle is to the lower limbs; the girdles are the parts of the appendicular skeleton that anchor the appendages to the axial skeleton.
In humans, the only true anatomical joints between the shoulder girdle and the axial skeleton are the sternoclavicular joints on each side. No anatomical joint exists between each scapula and the rib cage; instead the muscular connection or physiological joint between the two permits great mobility of the shoulder girdle compared to the compact pelvic girdle; because the upper limb is not usually involved in weight bearing, its stability has been sacrificed in exchange for greater mobility. In those species having only the scapula, no joint exists between the forelimb and the thorax, the only attachment being muscular.Shoulder joint
The shoulder joint (or glenohumeral joint from Greek glene, eyeball, + -oid, 'form of', + Latin humerus, shoulder) is structurally classified as a synovial ball and socket joint and functionally as a diarthrosis and multiaxial joint. It involves articulation between the glenoid cavity of the scapula (shoulder blade) and the head of the humerus (upper arm bone).
Due to the very loose joint capsule that gives a limited interface of the humerus and scapula, it is the most mobile joint of the human body.Spine of scapula
The spine of the scapula or scapular spine 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.Sprengel's deformity
Sprengel's deformity (also known as high scapula or congenital high scapula) is a rare congenital skeletal abnormality where a person has one shoulder blade that sits higher on the back than the other. The deformity is due to a failure in early fetal development where the shoulder fails to descend properly from the neck to its final position. The deformity is commonly associated with other conditions, most notably Klippel-Feil syndrome, congenital scoliosis including cervical scoliosis, fused ribs, the presence of an omovertebral bone and spina bifida. The left shoulder is the most commonly affected shoulder but the condition can be bilateral, meaning that both shoulders are affected. About 75% of all observed cases are girls. Treatment includes surgery in early childhood and physical therapy. Surgical treatment in adulthood is complicated by the risk of nerve damage when removing the omovertebral bone and when stretching the muscle tissue during relocation of the shoulder.Superior transverse scapular ligament
The superior transverse ligament (transverse or suprascapular ligament) converts the scapular notch into a foramen or opening.
It is a thin and flat fascicle, narrower at the middle than at the extremities, attached by one end to the base of the coracoid process and by the other to the medial end of the scapular notch.
The suprascapular nerve runs through the foramen; the transverse scapular vessels cross over the ligament.
The ligament can become ossified and impinge the underlying suprascapular nerve. This may cause paralysis of both supraspinatus and infraspinatus muscles.Trapezius
The trapezius (or trapezoid) is a large paired surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports the arm.
The trapezius has three functional parts: an upper (descending) part which supports the weight of the arm; a middle region (transverse), which retracts the scapula; and a lower (ascending) part which medially rotates and depresses the scapula.Winged scapula
A winged scapula (scapula alata) is a skeletal medical condition in which the shoulder blade, or shoulder bone, protrudes from a person’s back in an abnormal position.
In rare conditions it has the potential to lead to limited functional activity in the upper extremity to which it is adjacent. It can affect a person’s ability to lift, pull, and push weighty objects. In some serious cases, the ability to perform activities of daily living such as changing one’s clothes and washing one’s hair may be hindered. The name of this condition comes from its appearance, a wing-like resemblance, due to the medial border of the scapula sticking straight out from the back. Scapular winging has been observed to disrupt scapulohumeral rhythm, contributing to decreased flexion and abduction of the upper extremity, as well as a loss in power and the source of considerable pain. A winged scapula is considered normal posture in young children, but not older children and adults.