Shoulder Joint: Anatomy

Bones

Clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture

• The only horizontal long bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types in the body
• S-shaped, connects the upper limb with the axial Axial Computed Tomography (CT) skeleton
• Along with the scapula, forms the pectoral girdle
• Landmarks and articulations:
  • Medially articulates with the sternum Sternum A long, narrow, and flat bone commonly known as breastbone occurring in the midsection of the anterior thoracic segment or chest region, which stabilizes the rib cage and serves as the point of origin for several muscles that move the arms, head, and neck. Chest Wall: Anatomy to form the sternoclavicular joint Sternoclavicular Joint Examination of the Upper Limbs
  • Laterally articulates with the scapula to form the acromioclavicular joint Acromioclavicular joint The gliding joint formed by the outer extremity of the clavicle and the inner margin of the acromion process of the scapula. Examination of the Upper Limbs

Scapula

• Flat, triangular-shaped, with 3 angles, 3 borders, and an anterior and posterior surface
• Along with the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture, it forms the shoulder or pectoral girdle, connecting the upper limb to the trunk.
• Landmarks and articulations:
  • Glenoid cavity: lateral, articulates with the head of the humerus Head of The Humerus The upper rounded extremity of the humerus fitting into the glenoid cavity of the scapula. Arm: Anatomy to form the glenohumeral joint
  • Acromion: continuation of the scapular spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy, articulates with the lateral end of the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture to form the acromioclavicular joint Acromioclavicular joint The gliding joint formed by the outer extremity of the clavicle and the inner margin of the acromion process of the scapula. Examination of the Upper Limbs
  • Coracoid process: anterior, hook-shaped, place of attachment for multiple muscles and stabilizing ligaments

Humerus Humerus Bone in humans and primates extending from the shoulder joint to the elbow joint. Arm: Anatomy

• Bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types of the upper arm Upper Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy
• The proximal end comprises the head, the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, the greater and lesser tubercles, and the shaft.
• Landmarks and articulations:
  • Head of the humerus Head of The Humerus The upper rounded extremity of the humerus fitting into the glenoid cavity of the scapula. Arm: Anatomy: spherical, articulates with the glenoid cavity
  • Tubercles: greater is lateral, lesser is anterior. The supraspinatus, infraspinatus, and teres minor rotator cuff muscles attach to the greater tubercle, while the subscapularis attaches to the lesser tubercle.

Joints

Acromioclavicular (AC) joint

• Type of joint: plane synovial joint Synovial joint Jaw and Temporomandibular Joint: Anatomy between the acromion and the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture
• Function: allows for motion between the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture and scapula during arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy movement
• Ligaments: named according to their anatomical insertions
  • Acromioclavicular ligament: reinforces the superior part of the joint capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides and resists anteroposterior displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms at the AC joint
  • Coracoclavicular ligament: consists of the trapezoid and conoid ligaments and resists vertical and rotational displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms of the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture relative to the scapula

Glenohumeral joint

• Type of joint: synovial ball-and-socket joint between the head of the humerus Head of The Humerus The upper rounded extremity of the humerus fitting into the glenoid cavity of the scapula. Arm: Anatomy and the glenoid cavity of the scapula
• Function: most mobile joint in the body with multiple degrees of motion: flexion Flexion Examination of the Upper Limbs and extension Extension Examination of the Upper Limbs, abduction Abduction Examination of the Upper Limbs and adduction Adduction Examination of the Upper Limbs, medial and lateral rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays, and circumduction of the shoulder
• Ligaments and supporting structures:
  • Fibrous capsule Fibrous capsule Hip Joint: Anatomy: extends from the anatomical neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess of the humerus Humerus Bone in humans and primates extending from the shoulder joint to the elbow joint. Arm: Anatomy to the rim of the glenoid 
  • Glenoid labrum: fibrocartilaginous, meniscus-like structure that deepens the glenoid cavity
  • Ligaments: named according to their anatomical insertions
    • Coracoacromial ligament: resists superior displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms of the humeral head Humeral head The upper rounded extremity of the humerus fitting into the glenoid cavity of the scapula. Arm: Anatomy from the glenoid cavity 
    • Coracohumeral ligament: resists superior and inferior displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms and reinforces the anterior portion of the joint capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides
    • Glenohumeral ligaments: consists of superior, middle, and inferior bands and stabilizes the joint during adduction Adduction Examination of the Upper Limbs, abduction Abduction Examination of the Upper Limbs, and external rotation External Rotation Examination of the Upper Limbs, depending on the position of the shoulder
    • Transverse humeral ligament: maintains the long head of the biceps Biceps Arm: Anatomy tendon within the bicipital groove
  • Subacromial bursa:
    • Synovial cavity located inferior to the acromion and coracoid and superior to the supraspinatus/infraspinatus tendons
    • The function of the bursa is to decrease friction and facilitate movement between these structures during movement of the shoulder.

Sternoclavicular (SC) joint

• Type of joint: synovial saddle joint between the sternum Sternum A long, narrow, and flat bone commonly known as breastbone occurring in the midsection of the anterior thoracic segment or chest region, which stabilizes the rib cage and serves as the point of origin for several muscles that move the arms, head, and neck. Chest Wall: Anatomy and medial clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture
• Primary skeletal attachment between the axial Axial Computed Tomography (CT) skeleton and upper limb
• Function: allows for motion of the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture in multiple planes
• Ligaments:
  • Sternoclavicular ligament: primarily provides anterior/posterior stabilization and resists superior displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms
  • Costoclavicular ligament: anchors clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture to the first rib and resists clavicular elevation
  • Interclavicular ligament: strengthens the capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides and resists downward displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms of the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture

Scapulothoracic articulation

• Not a true synovial joint Synovial joint Jaw and Temporomandibular Joint: Anatomy
• Function:
  • Articulation between the concave anterior scapula and convex surface of the posterior thorax
  • Movement of the scapula on the thorax at this articulation requires movement at the AC joint and SC joint.

Anterior Axioappendicular Muscles

The anterior axioappendicular muscles function to move the pectoral girdle, stabilize the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture, and move the upper arm Upper Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy.

Posterior Axioappendicular Muscles

The posterior axioappendicular muscles stabilize and move the scapula and consist of a superficial and a deep layer.

Superficial or extrinsic layer

Deep or intrinsic layer

The deep or intrinsic layer consists of 6 muscles:

• Deltoid
• Teres major
• Supraspinatus
• Infraspinatus
• Teres minor
• Subscapularis

Scapulohumeral Muscles

The scapulohumeral muscles stabilize the glenohumeral joint by connecting the humerus Humerus Bone in humans and primates extending from the shoulder joint to the elbow joint. Arm: Anatomy to the scapula, including the rotator cuff muscles.

Rotator cuff muscles

Rotator cuff muscles stabilize the shoulder joint Shoulder joint The articulation between the head of the humerus and the glenoid cavity of the scapula. Examination of the Upper Limbs and prevent detachment of the head of the humerus Head of The Humerus The upper rounded extremity of the humerus fitting into the glenoid cavity of the scapula. Arm: Anatomy from the glenoid cavity via “concavity compression Compression Blunt Chest Trauma,” especially during abduction Abduction Examination of the Upper Limbs of the arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy.

Mnemonic

To recall the rotator cuff muscles, remember “SITS”:

S: Supraspinatus

I: Infraspinatus

T: Teres minor

S: Subscapularis

Clinical Relevance

The following conditions are common conditions associated with the shoulder:

• Shoulder dislocation: the separation of the head of the humerus Head of The Humerus The upper rounded extremity of the humerus fitting into the glenoid cavity of the scapula. Arm: Anatomy from the glenoid cavity. The glenohumeral joint is the most commonly dislocated joint. The vast majority of these dislocations are anterior-inferior (95%). Presents as severe shoulder pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and restricted range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs.
• Rotator cuff pathology: consists of a tear of one or more of the tendons of the 4 rotator cuff muscles. The supraspinatus is the most commonly torn rotator cuff tendon. May be associated with trauma or repeated activities. Presents with severe pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways or discomfort, loss of strength, and restricted range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs. These injuries may require surgical repair.
• SLAP SLAP Chronic Shoulder Pain (Superior Labral tear from Anterior to Posterior) lesion: consists of injury to the glenoid labrum. Presents as dull pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, discomfort, decreased range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs and strength, joint instability, and change in velocity in overhead athletes.
• Subacromial bursitis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the bursa located between the acromion and the deltoid muscle superficially and the supraspinatus muscle. Often caused by repetitive overhead motion. Presents as pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, swelling Swelling Inflammation, loss of strength, and stiffness of the shoulder. Can progress to impingement syndrome.
• Impingement syndrome: a spectrum of clinical manifestations caused by the compression Compression Blunt Chest Trauma of tissues as they pass through the subacromial space. Impingement syndrome can progress to a rotator cuff tear. Caused by many etiologies, including repetitive overhead motions or any condition that further narrows the subacromial space. Impingement syndrome presents as shoulder pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways with overhead motions (“painful arc”), restriction of range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs, loss of strength, and pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways when sleeping on the shoulder.
• Adhesive capsulitis Adhesive Capsulitis Chronic Shoulder Pain: also known as “ frozen shoulder Frozen Shoulder Chronic Shoulder Pain,” the painful loss of motion of the shoulder due to inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans of the fibrous capsule Fibrous capsule Hip Joint: Anatomy; may be associated with diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus, thyroid Thyroid The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland: Anatomy disease, trauma, or prolonged immobilization Immobilization Delirium.