Podcast
Questions and Answers
Which joint connects the clavicle to the scapula?
Which joint connects the clavicle to the scapula?
What movement is described as "horizontal adduction" in the text?
What movement is described as "horizontal adduction" in the text?
What is the type of movement that involves combining all three cardinal axes of motion in the shoulder complex?
What is the type of movement that involves combining all three cardinal axes of motion in the shoulder complex?
Which of the following joints is directly involved in the movement of lateral and medial rotation of the humerus?
Which of the following joints is directly involved in the movement of lateral and medial rotation of the humerus?
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What is the name of the joint formed between the sternum and the clavicle?
What is the name of the joint formed between the sternum and the clavicle?
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Which joint serves as the only structural attachment of the clavicle, scapula, and upper extremity to the axial skeleton?
Which joint serves as the only structural attachment of the clavicle, scapula, and upper extremity to the axial skeleton?
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Which of these movements is NOT a cardinal plane motion in the shoulder complex?
Which of these movements is NOT a cardinal plane motion in the shoulder complex?
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Which joint does not have the characteristics of a synovial joint?
Which joint does not have the characteristics of a synovial joint?
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The subacromial 'functional joint' is formed by the movement of what structure under the coracoacromial arch?
The subacromial 'functional joint' is formed by the movement of what structure under the coracoacromial arch?
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What is the primary function of the scapulothoracic joint, despite not being a true joint?
What is the primary function of the scapulothoracic joint, despite not being a true joint?
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Which joint is considered part of the shoulder girdle?
Which joint is considered part of the shoulder girdle?
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What is the range of motion for shoulder extension (horizontal abduction) as stated in the text?
What is the range of motion for shoulder extension (horizontal abduction) as stated in the text?
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What is the primary function of the scapulothoracic joint?
What is the primary function of the scapulothoracic joint?
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Which of the following accurately describes the "cross-body function of the arm" as mentioned in the text?
Which of the following accurately describes the "cross-body function of the arm" as mentioned in the text?
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What is the primary role of the scapulohumeral rhythm?
What is the primary role of the scapulohumeral rhythm?
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Which joint is responsible for the majority of the shoulder girdle's osteokinematic movements?
Which joint is responsible for the majority of the shoulder girdle's osteokinematic movements?
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What is the relationship between the three joints of the shoulder complex (SC, AC, and GH)?
What is the relationship between the three joints of the shoulder complex (SC, AC, and GH)?
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During shoulder abduction, which joint experiences the greatest range of motion?
During shoulder abduction, which joint experiences the greatest range of motion?
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What is the primary role of the clavicle during the scapulohumeral rhythm?
What is the primary role of the clavicle during the scapulohumeral rhythm?
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What is the main reason for the acromioclavicular joint's displacement during shoulder girdle movements?
What is the main reason for the acromioclavicular joint's displacement during shoulder girdle movements?
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Which muscle is primarily responsible for upward rotation of the scapula?
Which muscle is primarily responsible for upward rotation of the scapula?
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The shoulder complex is made up of the shoulder and the shoulder girdle. Which joint is considered part of the shoulder complex but not the shoulder girdle?
The shoulder complex is made up of the shoulder and the shoulder girdle. Which joint is considered part of the shoulder complex but not the shoulder girdle?
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What term refers to the synchronized movement of the scapula and humerus, allowing for large ranges of motion at the shoulder?
What term refers to the synchronized movement of the scapula and humerus, allowing for large ranges of motion at the shoulder?
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Which of the following muscles acts as a primary mover (agonist) during shoulder abduction?
Which of the following muscles acts as a primary mover (agonist) during shoulder abduction?
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Which of the following is NOT a component of the shoulder complex?
Which of the following is NOT a component of the shoulder complex?
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Which phase of the scapulohumeral rhythm involves the greatest amount of scapular upward rotation?
Which phase of the scapulohumeral rhythm involves the greatest amount of scapular upward rotation?
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Which of the following joints contributes the least amount of motion to the overall shoulder abduction movement?
Which of the following joints contributes the least amount of motion to the overall shoulder abduction movement?
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What is the primary function of the secondary movers in muscular action?
What is the primary function of the secondary movers in muscular action?
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Which of these joints exhibits incongruent articular surfaces and relies on a disc for stability?
Which of these joints exhibits incongruent articular surfaces and relies on a disc for stability?
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What is the main function of the glenohumeral capsule?
What is the main function of the glenohumeral capsule?
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Which of these ligaments is NOT involved in reinforcing the glenohumeral joint?
Which of these ligaments is NOT involved in reinforcing the glenohumeral joint?
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What is the role of the rotator cuff muscles in glenohumeral joint stability?
What is the role of the rotator cuff muscles in glenohumeral joint stability?
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Which of these actions does NOT contribute to the stability of the glenohumeral joint?
Which of these actions does NOT contribute to the stability of the glenohumeral joint?
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What is the primary function of the glenohumeral joint?
What is the primary function of the glenohumeral joint?
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What type of joint is the glenohumeral joint categorized as?
What type of joint is the glenohumeral joint categorized as?
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Which of the following motions occur in the sagittal plane at the glenohumeral joint?
Which of the following motions occur in the sagittal plane at the glenohumeral joint?
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What is the name of the phenomenon that describes the automatic medial rotation of the limb on its long axis during abduction and extension?
What is the name of the phenomenon that describes the automatic medial rotation of the limb on its long axis during abduction and extension?
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How many degrees of freedom does the glenohumeral joint have?
How many degrees of freedom does the glenohumeral joint have?
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What is the 'Codman's Paradox' commonly observed in the glenohumeral joint?
What is the 'Codman's Paradox' commonly observed in the glenohumeral joint?
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Why is the 'Codman's Paradox' considered a 'false paradox'?
Why is the 'Codman's Paradox' considered a 'false paradox'?
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Which structure is responsible for the articulation of the glenohumeral joint?
Which structure is responsible for the articulation of the glenohumeral joint?
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What is the approximate range of motion for internal rotation of the glenohumeral joint?
What is the approximate range of motion for internal rotation of the glenohumeral joint?
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What does the term 'biconvex' refer to in the context of the glenohumeral joint?
What does the term 'biconvex' refer to in the context of the glenohumeral joint?
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Flashcards
Incongruency
Incongruency
Insufficient contact between joint surfaces leading to instability.
Glenohumeral Joint Structure
Glenohumeral Joint Structure
A joint with a large, loose capsule, providing necessary movement but little stability.
Coracohumeral Ligament
Coracohumeral Ligament
A ligament that supports the glenohumeral joint, originating from the coracoid process.
Rotator Cuff Muscles
Rotator Cuff Muscles
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Glenoid Labrum
Glenoid Labrum
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Scapulohumeral Rhythm
Scapulohumeral Rhythm
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GH Joint Abduction
GH Joint Abduction
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Scapulothoracic Upward Rotation
Scapulothoracic Upward Rotation
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Phases of Shoulder Abduction
Phases of Shoulder Abduction
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Prime Mover (Agonist)
Prime Mover (Agonist)
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Antagonist Muscle
Antagonist Muscle
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Synergist Muscle
Synergist Muscle
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Secondary Mover
Secondary Mover
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Scapulothoracic joint
Scapulothoracic joint
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Subacromial functional joint
Subacromial functional joint
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Glenohumeral joint (GH)
Glenohumeral joint (GH)
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Acromioclavicular joint (AC)
Acromioclavicular joint (AC)
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Sternoclavicular joint (SC)
Sternoclavicular joint (SC)
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Shoulder complex components
Shoulder complex components
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Osteokinematic movements
Osteokinematic movements
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Movement of scapula
Movement of scapula
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Coracoacromial arch
Coracoacromial arch
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Muscles of the shoulder girdle
Muscles of the shoulder girdle
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Vertical Axis
Vertical Axis
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Flexion
Flexion
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Extension
Extension
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Humerus Rotation
Humerus Rotation
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Circumduction
Circumduction
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Anatomical Base
Anatomical Base
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Shoulder Complex
Shoulder Complex
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Sternoclavicular Joint
Sternoclavicular Joint
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Acromioclavicular Joint
Acromioclavicular Joint
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Glenohumeral Joint
Glenohumeral Joint
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Degrees of freedom
Degrees of freedom
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Main motions of GH joint
Main motions of GH joint
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Abduction
Abduction
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Codman's Paradox
Codman's Paradox
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Conjunct rotation
Conjunct rotation
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Internal rotation
Internal rotation
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External rotation
External rotation
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Three degrees of freedom in joints
Three degrees of freedom in joints
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Study Notes
Upper Extremities - Functional B
- Lecturer: Beáta Seregély, assistant lecturer
- Contact: [email protected]
- Location: Semmelweis University Faculty of Health Sciences Department of Physiotherapy.
The Free Upper Limb
- Main Functions: reaching for, grabbing, holding, manipulating, releasing an object, supporting, clinging.
- Cognition Tool: The free upper limb, along with the visual system, is the most important tool of cognition.
- Two Parts: Divided into the hand (most complex part of the locomotor system) and the arm, whose primary function is to position the hand in space.
The Shoulder Complex - Mobility
- Freedom of Movement: Achieved through the shoulder-shoulder girdle complex, connecting the upper limb to the trunk, forming the trunk-arm-hand kinetic chain.
- Mobility Design: The articular structures of the shoulder complex are designed primarily for mobility.
- Dynamic Stability: Muscles provide dynamic stability needed for free movement, and play an important role in generating movements
- Stabilizing Role: Joint and surrounding structures (capsule, ligaments) have a less stabilizing role in the shoulder-shoulder girdle complex.
The Shoulder Complex - Mobility (cont.)
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Degrees of Freedom: From an osteokinematic point of view, the shoulder is a free joint with 3 degrees of freedom, allowing for orientation in 3 planes of space.
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Coronal Plane Movements: Flexion (180°) and extension (45-50°) occur in the sagittal plane. Abduction (away from the body) (180°) and adduction (toward the body) (~30° in front of the body) occur in the coronal (frontal) plane.
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Horizontal Plane Movements: Flexion (horizontal adduction) (140°) and extension (horizontal abduction) (30°-40°) occur in the horizontal plane.
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Humerus Rotation: Lateral (80°-90°) and medial (70°-110°) rotation, dependent on humerus position.
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Circumduction: Combines movements about three cardinal axes, describing a conical surface in space.
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Accessibility Sector: Describes a spherical sector of accessibility for the hand, allowing it to reach all parts of the body without trunk displacement.
The Shoulder Complex - Components
- Segments: Clavicle, scapula, and humerus, connected to the trunk through the sternum.
- Interdependent Linkages: Sternoclavicular (SC) joint, Acromioclavicular (AC) joint, Glenohumeral (GH) joint.
- Scapulothoracic Joint (ST): Frequently described as a "functional" joint, not a synovial joint.
- Subacromial (Suprahumeral) "Functional Joint": Part of the shoulder complex, created by the movement of the humeral head below the coracoacromial arch.
The Shoulder Girdle
- Structural Attachment: The SC joint serves as the only structural attachment of the clavicle, scapula, and upper extremity to the axial skeleton.
- Muscle Location: The majority of muscles generating shoulder girdle movements are located on the trunk, moving the scapula and creating clavicular displacements through the tight acromioclavicular joint (in the sternoclavicular joint).
- Osteokinematic Movements: Performed in the sternoclavicular joint, observed through acromion and scapular displacements
The Shoulder Girdle – The Function
- Connection: The primary function of the shoulder girdle is to connect the trunk and the arm.
- Purpose of Displacements: Increases the range of motion of the shoulder complex and adjusts the glenoid cavitas for optimal shoulder joint movements.
- Closed Kinematic Chain: Any displacement of one joint generates movements in the whole system.
The Shoulder Girdle – Sternum
- Osteologic Features: Manubrium, clavicular facets, costal facets, jugular notch, (body), (xiphoid process).
- Originating Muscles: Sternocleidomastoid, Pectoralis major, Subclavius.
The Shoulder Girdle – Clavicle
- Osteologic Features: Shaft (S shaped), Sternal end, Costal facet, Costal tuberosity, Acromial end, Acromial facet, Conoid tubercle, Trapezoid line.
- Originating Muscles: Sternocleidomastoid, Pectoralis major, Anterior deltoid, Subclavius, Upper trapezius.
The Shoulder Girdle – Scapula
- Osteologic Features: Angles (inferior, superior, lateral), Medial (vertebral) or Lateral (axillary) border, Superior border, Supraspinous fossa, Infraspinous fossa, Spine, Root of the spine, Acromion.
- Originating Muscles: Supraspinatus, Infraspinatus, Posterior deltoid, Teres minor and major, Latissimus dorsi, Lower and middle trapezius, Levator scapulae, Rhomboid minor and major.
The Shoulder Girdle - Scapula (cont.)
- Osteologic Features: (cont.) Clavicular facet, Glenoid fossa (6°-7° retroverted), Supraglenoid and infraglenoid tubercles, Coracoid process, Subscapular fossa
- Originating Muscles: (cont.) Middle deltoid, Biceps short head, Coracobrachialis, Triceps long head Subscapularis, Serratus anterior, Pectoralis minor.
The Shoulder Girdle – Coracoid Process
- Originating Muscles: Biceps short head, Coracobrachialis
- Inserting Muscles: Pectoralis minor
- Attaching Ligaments: Coracohumeral, Coracoacromial, Coracoclavicular, Conoid, Trapezoid
The Shoulder Girdle – Humerus
- Proximal-to-Mid Features: Head of the humerus (one-third to one-half of a 3 cm sphere), Anatomic neck (45° superiorly to the shaft), Lesser tubercle and crest, Greater tubercle and crest, Intertubercular (bicipital) groove, Deltoid tuberosity.
- Originating Muscles: Supraspinatus, Subscapularis, Pectoralis major, Latissimus dorsi, Teres major, Deltoid, Coracobrachialis.
The Shoulder Girdle - Humerus (cont.)
- Originating Muscles: (cont) Teres minor, Infraspinatus, Supraspinatus, Subscapularis.
The Shoulder Girdle - Humerus (cont.)
- Osteological Features: (cont.) Head, Lesser tubercle, Greater tubercle, upper, middle, and lower facets on the greater tubercle, intertubercular (bicipital) groove.
- Originating Muscles: Teres minor, Infraspinatus, Supraspinatus, Subscapularis.
The Shoulder Girdle - Humerus (cont.)
- Inclination Angle: The humeral head makes a 135° angle with the humeral shaft and a 30° angle with the coronal plane.
- Retroversion Angle: The humeral head makes a 30° angle with the coronal plane.
- Declination Angle: The anatomical neck makes a 45° angle with the horizontal plane.
- Tuberosities: The two tuberosities (lesser and greater) receive periarticular muscle insertions.
The Shoulder Girdle - Humerus (cont.)
- Head: The humeral head aligns superiorly, medially, and posteriorly
- Radius: A radius of 3 cm.
- Shape: The third of a sphere.
- Alignment: Anatomical neck forms a 45-degree angle to the humeral shaft, and the head forms a 135-degree angle with the latter.
The Shoulder Girdle - Scapula Positioning
- Extends: From the second to the seventh rib.
- Superior-Medial Angle: Corresponds to the first thoracic spinous process or the second rib.
- Spine Tip: Located at the level of the third spinous process.
- Medial Border: Located 5-6 cm from the interspinous line.
- Inferior Angle: Located 7 cm from the interspinous line, corresponding to the seventh rib.
The Scapula-Thoracic "Functional Joint"
- Gliding Planes: The joint consists of two gliding planes, formed by the serratus anterior sheet extending from the medial scapular border to the lateral thoracic wall.
- Gliding Spaces: Separated by the subscapularis and serratus anterior (space 1) and the thoracic wall and serratus anterior (space 2).
Misalignments of the Scapula
- Images of postural misalignments are provided.
Scapula Mobility
- Primary Movements: Elevation/depression, protraction/retraction (abduction), upward/downward rotation.
Terminology Describing Primary Movements
- Elevation: Scapula slides superiorly on the thorax.
- Depression: Scapula slides inferiorly on the thorax.
- Protraction: Medial scapular border slides anterior-laterally on the thorax away from the midline.
- Retraction: Medial scapular border slides posterior-medially on the thorax toward the midline.
- Upward Rotation: Inferior angle rotates superiorly and laterally.
- Downward Rotation: Inferior angle rotates inferiorly and medially.
Accessory Motions of the Scapula
- AC Joint Motions: Upward/downward rotation of scapula at the AC joint.
- Ap Axis: Passes between the joint and the coracoclavicular ligament.
- Horizontal Plane Adjustments: medial border of the scapula pivots away and toward the thorax's posterior surface.
- Internal/External Rotation: Rotation around glenoid fossa.
- Scapular Winging: Loss of contact between the vertebral border of the scapula and the thorax.
Sternoclavicular (SC) Joint
- Complex Articulation: Involves the medial end of the clavicle, clavicular facet on the sternum, and superior border of the first rib cartilage.
- Appendicular and Axial Skeleton Link: Connects the appendicular skeleton (upper limb) with the axial skeleton (trunk).
- Saddle Shaped Surface: With an irregular saddle-shaped articular surface.
- Clavicle End Characteristics: Medial end of the clavicle convex along longitudinal diameter, slightly concave transversely.
- Sternum End Attributes: Sternal end of the clavicle and manubrium incongruent, little contact between articular surfaces.
Sternoclavicular Joint Stability - The Disc
- Superior Portion: Medial clavicle does not contact manubrium; attachment site for the SC joint disc and interclavicular ligament.
- Lower Portion: Attached to manubrium and the first costal cartilage; anterior and posterior aspects connect to the fibrous capsule.
- Stability Function: Increases joint congruence, absorbing forces from the lateral end of the clavicle.
- Medial Movement of Clavicle: Diagnol attachment prevents medial movement, preventing excessive pressure on manubrial facet.
Sternoclavicular Joint Stability - Capsule and Ligaments
- Fibrous Capsule: Surrounds the joint but relies on ligaments for support.
- Sternoclavicular Ligaments (Anterior and Posterior): Reinforce the capsule and check anterior/posterior movement of the medial clavicle end
- Costoclavicular Ligament: Strong ligament between the clavicle and first rib, with anterior/posterior lamina segments that check clavicle elevation and inferior gliding.
Sternoclavicular Joint Stability - Capsule and Ligaments (cont.)
- Interclavicular Ligament: Resists excessive distal clavicle depression and superior glide of the medial clavicle end.
- Protection: Prevents pressure on brachial plexus and subclavian artery.
- Support: Interclavicular ligament supports the weight of the upper extremity, or external loads.
Acromioclavicular (AC) Joint
- Articulation: Between the lateral end of the clavicle and the acromion of the scapula.
- Clavicular and Acromial Facets: The clavicular facet faces medially and slightly superiorly on the acromion, providing an attachment point.
- Articular Disc: Present in most cases, its form varies.
- Gliding or Plane Joint: With slightly convex or concave surfaces.
Acromioclavicular Joint - Stability
- Coracoclavicular Ligament (CCL): Stronger than other shoulder ligaments, absorbing more energy, resisting superior dislocation of the clavicle, and limiting upward rotation of the scapula at the AC joint.
- Medial Displacement Prevention: Tension applied through the coracoclavicular ligament prevents medial displacement of the scapula's acromion from the clavicle.
- Function: Critical in coupling posterior rotation of the clavicle to scapular rotation during upper extremity elevation.
Acromioclavicular Joint - Mobility
- Distinct Differences: The SC and AC joints have distinct functions.
- SC Joint Function: Permits extensive clavicle motion, guiding scapular movement.
- AC Joint Function: Allows subtle movements between the scapula and lateral clavicle end, optimizing mobility and fitting with the glenohumeral joint.
Muscle of the Shoulder Girdle - Brachial Plexus
- Nerves: Musculocutaneous, Axillary, Radial, Median, Ulnar.
- Cords: Lateral, medial, posterior.
- Subdivisions: Upper, middle, lower.
- Trunks: Superior, middle, inferior.
- Roots: C4-T1
Muscle of the Shoulder Girdle - Brachial Plexus - (cont.)
- Nerve Relations to Brachial Plexus: Provides specific nerve root pathways for supplying different primary shoulder muscles.
- Muscle Innervation: Details the correspondence between the nerves and the muscles they innervate.
Muscle Actions of the Shoulder Girdle
- Elevators (posterior aspect): Upper and Middle Trapezius, Levator scapulae, Rhomboids.
- Depressors (posterior aspect): Lower Trapezius, Latissimus dorsi, Pectoralis minor, Subclavius.
- Protractors/Abductors: Serratus anterior.
- Retractors/Adductors: Middle and Lower Traps, Rhomboids.
- Upward Rotators: Serratus anterior, upper and lower trapezius.
- Downward Rotators: Rhomboids, pectoralis minor, and levator scapulae.
Muscle Actions of the Shoulder Girdle (cont.)
- Elevators (posterior aspect - cont.): Trapezius (3 parts) elevates shoulder girdle, rotates scapula laterally and superiorly.
- Mid Trapezius: (1') adducts scapula.
- Lower Trapezius: (1") depresses scapula, rotates scapula laterally and superiorly.
- Rhomboids (major and minor): (2) adduct and elevates scapula, rotates medially and inferiorly; fixing the inferior angle against ribs.
- Levator Scapulae: (3) elevates scapula, rotates medially and inferiorly.
Muscle Actions of the Shoulder Girdle - (cont.)
- Depressors (posterior aspect): Lower trapezius depresses and laterally rotates the scapula.
- Latissimus Dorsi: (indirectly) depresses shoulder girdle by pulling humerus inferiorly.
- Pectoralis Minor: Depresses and medially rotates the scapula, pulling the posterior edge of the scapula away from the thorax.
- Subclavius: Depresses the clavicle, indirectly depressing the shoulder girdle, fixing the clavicle to the first rib and pressing it against the sterno-costo-clavicular joint.
Muscle Actions of the Shoulder Girdle - Lateral Aspect - Protractor
- Serratus Anterior: Lies on the deep surface of the scapula and spreads over the posterior lateral wall of the thorax.
- Upper Part (4): Runs horizontally, anteriorly drawing scapula anteriorly, laterally, and slightly elevating it
- Lower Part (4'): Runs obliquely, anteriorly and inferiorly, tilts the scapula superiorly, pulling the inferior angle laterally and causing the glenoid cavity to face superiorly.
Muscle Actions of the Shoulder Girdle - Lateral Aspect - Retractor
- Middle Trapezius, Rhomboids, Lower Trapezius: Contract synergistically, functioning as primary retractors of the scapula.
- Middle Trapezius: Has the most optimal line of force for retraction.
- Rhomboids and Lower Trapezius: Act as antagonists to each other to control retraction actions.
Misalignments of the Scapula
- Downward Rotated: Short levator scapulae and rhomboids; lengthened upper trapezius (serratus anterior)
- Depressed: Lengthened upper trapezius and short, or over working latissimus dorsi, pectoralis major
- Elevated: Short levator scapulae, upper trapezius, and lengthened serratus anterior.
- Adducted: Short rhomboids and trapezius; lengthened serratus anterior.
- Abducted: Short serratus ant., pectoralis major.
- Tilted: Short coracobrachialis, (biceps brachii short head, anterior deltoid and) combination
- Depressed and Tilted: combination
- Winged: Weak serratus anterior, hypertophey of the subscapularis, short upper trapezius.
The Glenohumeral (Shoulder) Joint
- Ball and Socket Synovial Joint: With three rotational and three translational degrees of freedom.
- Articulation: Composed of the large biconvex head of the humerus and the shallow biconcave glenoid fossa.
- Main Motions: Flexion, extension, abduction, adduction, internal/ external rotation.
The Codman's "Paradox"
- Limb Position: Initial position with the upper limb hanging vertically alongside the trunk, thumb anteriorly and palm medially.
- Abduction: Abducting the limb to 180 degrees.
- Extension: Extending the limb to 180 degrees in the sagittal plane.
- Return to Starting Position: The limb returns to the initial position with the palm facing laterally and thumb posteriorly.
- Automatic Medial Rotation: Due to automatic medial rotation of the limb on its long axis called conjunct rotation.
The Glenohumeral (Shoulder) Joint (cont.)
- Humeral Head Features: Faces superiorly, medially, and posteriorly.
- Radius: 3cm radius.
- Inclination Angle: 135 degree angle between the humeral head axis and the humeral shaft axis
- Retroversion Angle: 30 degree angle between the humeral head axis and the coronal plane
- Declination Angle: 45 degree angle between the anatomical neck and the humeral shaft.
- Tuberosities: Lesser and Greater tuberosities, for muscle attachments
The Glenohumeral (Shoulder) Joint (cont.)
- Glenoid Cavity: Lies at the superolateral angle of the scapula.
- Vertical and Transverse Concavity: Slightly biconcave.
- Humeral Head Convexity: Greater than the glenoid cavity.
- Longitudinal and Transverse Diameters: Humeral head diameter is larger than the glenoid fossa diameter.
- Glenoid Labrum: A ring of fibrocartilage that deepens the glenoid cavity for more congruent surface areas.
The Glenoid Labrum (Right Shoulder)
- Attachment Timing: origin of long head of biceps -12 hours, anterior parts -3 hours, between the 9 and 3-hour mark is loosely attached, Inferior portion is firmly attached and relatively immobile.
- Attachment Significance: Attaches to the glenohumeral ligaments and deepens the articular groove up to 50% to increase stability.
Incongruency
- Articular Surfaces: The humeral head is significantly larger and has a different curvature than the shallow glenoid cavity.
- Joint Contact: Bony contact alone cannot maintain joint congruency in dependent positions.
- Stability Mechanisms: Strong capsules and ligaments provide substantial stability to the joint.
Glenohumeral Capsule and Ligaments
- Capsule Structure: Large, loose capsule that is taut superiorly and slack in the anterior and inferior regions (axillary pouch).
- Laxity: Relative laxity is necessary for free movements.
- Reinforcement: Reinforced by coracohumeral and glenohumeral ligaments
- Long Biceps Tendon: Inserts into the supraglenoid tubercle of the scapula.
- Intracapsular Position: Important for articulation.
The Coracohumeral Ligament
- Origination: Originates from the coracoid process, with two bands.
- Posterior Band: Inserts into the edge of the supraspinatus and greater tubercle, joining the superior GH ligament.
- Anterior Band: Inserts into the subscapularis and the lesser tubercle.
- Function: Plays a critical role in limiting inferior translation of the humeral head in the dependent arm and preventing superior translation when the rotator cuff muscles are impaired.
The Glenohumeral Ligaments
- Composition: Three parts: supraglenoid suprahumeral superior (1), supraglenoid prehumeral middle (10) band, and preglenoid subhumeral inferior (11).
- Components: Anterior, Posterior bands and a sheet that connects them called the axillary pouch
- Weak Points: Two areas of potential weakness: the foramen of Weitbrecht and the foramen of Rouviere.
The Superior Glenohumeral Ligament
- Proximal Attachment: Near the supraglenoid tubercle about the 1 o'clock position
- Biceps Tendon Attachment: Also near the anatomic neck
- Stability: Supports the humeral head resisting movement during external rotation.
- Slackening beyond 35-45 Degrees: Significantly slackens during abduction beyond 35-45 degrees, and is taut at the start and end of adduction.
The Middle Glenohumeral Ligament
- Proximal Attachment: Attaches to the superior and middle aspects of the anterior glenoid rim, approximately 2-4 o'clock.
- Capsule and Subscapularis Muscle: Blends with the anterior capsule and the subscapularis muscle, then attaches to the anterior aspect of the anatomical neck.
- Function: Provides substantial anterior restraint to the GH joint
- Slackening during Internal Rotation: During internal rotation, the ligament readily slackens.
The Inferior Glenohumeral Ligament
- Proximal Attachment: Attaches proximally along the anterior-inferior rim of the glenoid fossa (approximately at 4–8 o'clock).
- Posterior-Inferior Attachment: Also attaches as a sheet to the posterior-inferior margins of the anatomical neck, forming a sling-like structure
- Stability: Important for stability and support for the suspended humeral head, resisting inferior and anterior/posterior translations.
- Tightness in Abducted Position: Taut during abduction, particularly important in limiting the excessive movement.
The Coracoacromial Arch
- Component Structures: Coracoid process, acromion, and coracoacromial ligament.
- Functional "Roof": Spanning the two bony structures
- Subacromial Space Contents: Contains supraspinatus muscle and tendon, subacromial bursa, long head of the biceps tendon, and a portion of the superior capsule.
- Protection: Prevents dislocating the humeral head superiorly
The Bursae
- Multiple Bursae: Located around the shoulder, with some being extensions of the GH joint synovial membrane (like subscapular bursa).
- Function: Reduce friction between structures like tendons, capsules, muscles, and bones.
- Critical Bursae: Subacromial (SbA) and subdeltoid (SD) bursae are the most significant, protecting supraspinatus and deltoid/supraspinatus from the acromion and the humeral head, respectively
The Physiological Alignment of the Humerus
- Postural Conditions: Neutral rotational/positional spinal alignment for the dorsal spine and scapula alignment
- Humeral Head Position: Less than one-third of the humeral head is in front of the acromion.
- Humeral Alignment: The upper and lower portions of the humerus are positioned on a vertical straight line.
Static Stabilization of the GH Joint in Neutral Position
- Gravity Effect: Gravity's downward force on the humerus creates a downward translatory force.
- Passive Stabilizing Forces: The line of gravity, along with passive tension in the structures of the rotator interval capsule, superior GH ligament, and coracohumeral ligament (when the arm is in the neutral position) combine to compress the humeral head into the lower portion of the glenoid fossa.
- Intra-Articular Pressure: Negative intra-articular pressure, along with glenoid inclination, provides considerable stability.
Static Stabilization of the GH Joint in Neutral Position (cont.)
- Muscle Roles: The supraspinatus is recruited when passive forces are inadequate for static stabilization.
- Upward Directed Forces: Muscles with upward directed forces may contribute to stability (deltoid, supraspinatus, biceps brachii, and triceps brachii long heads).
Mobility - Osteokinematics
- Degrees of Freedom: GH joint rotates in all three planes, so it has three degrees of freedom.
- Main Rotational Movements: Flexion/extension in the sagittal plane, abduction/adduction in the frontal plane, and internal/external rotation in the horizontal plane.
- Fourth Motion: Horizontal adduction and abduction (around a vertical axis of rotation).
Mobility - Arthrokinematics
- Spin: A pure rotational motion.
- Rolling: Combination of translation and rotation (different points on the rolling object meet different surfaces).
- Sliding/Gliding: Pure translation (sliding of one component over another).
Mobility - Arthrokinematics (Abduction/Adduction)
- Abduction: Convex head of the humerus rolls superiorly and slides inferiorly
- Adduction: Reverse motion; the convex head of the humerus rolls and slides inferiorly.
Mobility - Arthrokinematics (Scapular Plane Abduction/Horizontal Adduction/Horizontal Abduction)
- Scapular Plane Abduction: More natural than frontal plane, preventing impingement and maintaining a straight line.
- Abduction Completion: Completed by adding external rotation.
- Horizontal Abduction: Head of the humerus rolling and sliding posteriorly
- Horizontal Adduction: Reverse of horizontal abduction.
Mobility - Arthrokinematics (Flexion/Extension/External/Internal Rotation)
- Flexion: Spinning motion of the humeral head. Posterior capsule tension may cause anterior translation of the humerus.
- Extension: Reverse motion causing anterior tilting of the scapula.
- External Rotation: Humeral head rolls posteriorly and slides anteriorly in the glenoid fossa.
- Internal Rotation: Reverse of external rotation.
Mobility - Arthrokinematics
- Anterior/Posterior Translation: Provoked by abduction, external rotation, horizontal abduction, flexion, and internal rotation.
- Stability: Passive elements of the capsule and ligaments are weakest in ventral direction. This can lead to luxation in extreme abduction and external rotation.
Dynamic Stabilization of the GH Joint
- Dynamic Stability: Achieved while the joint is moving, through the interplay of activated muscles and stretched capsular ligaments on the glenoid fossa.
Dynamic Stabilization of the GH Joint - Glenohumeral Ligaments
- Abduction: Superior band and coracohumeral ligament are relaxed, middle and inferior bands become taut.
- Adduction: Superior band becomes taut, both are taut by the range of motion.
- Lateral Rotation: Stretches all three bands, and
- Medial Rotation: Relaxes the bands.
Dynamic Stabilization of the GH Joint - Coracohumeral Ligament
- Neutral Rotational Position: The anterior (lesser tub.) and posterior (greater tub.) bands of the coracohumeral ligament become taut.
- Flexion: Tension develops in the posterior (greater tub.) band.
- Lateral Rotation: Stretches the anterior (lesser tub.) band.
- Medial Rotation: Stretches the posterior (greater tub.) band.
Dynamic Stabilization of the GH Joint - Dynamic Stabilizers
- Deltoid Muscle: Prime mover for abduction and flexion
- Muscle Action Line (FD/Fy): Resolved into parallel (Fx) and perpendicular (Fy) components.
- Translational Component: Large superiorly directed component.
Dynamic Stabilization of the GH Joint- Dynamic Stabilizers (cont.)
- Rotator Cuff Muscles (SITS): Supraspinatus, infraspinatus, teres minor, subscapularis muscles work together to offset the superior translator force
- Blended with Capsule: Important to note the blending with and reinforcement of the GH capsule by these rotator cuff muscles.
Scapulohumeral Rhythm
- Ratio: 2:1 ratio (2 degrees of GH joint abduction for every 1 degree of scapulothoracic upward rotation).
- Large ROM: Distributes motion between joints to permit a large range of motion with reduced compromise of stability.
- Glenoid Fossa Placement: In consistent optimal positioning to maximize the head of the humerus.
- Shear Forces Control: Reduces shear forces and maintains a good length-tension relationship in the muscles.
Scapulohumeral Rhythm - Phases
- Phase 1: 30° humerus abduction, minimal scapula movement (setting phase), mild clavicle elevation (0-5 degrees)
- Phase 2: 40° humerus abduction, 20-30 degrees scapula rotation, little protraction or elevation, 15 degrees clavicle elevation.
- Phase 3: 60° humerus abduction and 90 degrees lateral rotation. 30 degrees scapula rotation, 30-50 degrees posterior clavicle rotation (after elevation to 15 degrees). Serratus anterior rotates scapula to enable full upward rotation
Muscle Actions by Planes - Elevation
- Muscles Elevate Humerus: Anterior and middle deltoids, supraspinatus, coracobrachialis, biceps brachii.
- Scapular Muscle Coordination: Serratus anterior, trapezius control upward rotation.
- Rotator Cuff Role: Dynamic stability and arthrokinematics at the GH joint.
Muscle Actions by Planes - Abduction (0-180 Degrees)
- Prime Movers: Middle deltoid and supraspinatus for abducting the GH joint.
- Secondary Movers (Synergists): Anterior and posterior deltoids, biceps brachii.
- Stabilizing Synergists: Infraspinatus, teres minor, subscapularis support.
- Antagonists: Latissimus dorsi, teres major, long head of the triceps, pectoralis major.
- Paravertebral Muscle Role: Contribute at the end of the glenohumeral movement range.
Muscle Actions by Planes - Abduction (0-180 degrees)
- External Rotation of Upper Arm/Scapula: The scapula rotates outwardly, and superiorly while the clavicle rotates posteriorly
- Prime Muscles: Supraspinatus, Middle deltoid.
- Secondary Movers (Synergists): Anterior and posterior deltoids, biceps brachii.
- Stabilizing Muscles: Infraspinatus, teres minor, subscapularis
- Antagonists: Latissimus dorsi, teres major, long head of the triceps, and pectoralis major
Muscle Actions by Planes - Flexion (0-180 Degrees)
- Prime Movers: Anterior deltoid, coracobrachialis, long head of biceps.
- Secondary Movers: Pectoralis major clavicular fibers
- Antagonists: Teres minor, teres major, infraspinatus.
- Same Motions as Abduction: Similar motions to scapular actions.
Muscle Actions by Planes - Adduction (180-0 Degrees)
- Primary Adductors: Latissimus dorsi, teres major, sternocostal head of pectoralis major.
- Secondary Movers (Synergists): Posterior deltoid, infraspinatus, teres minor, and long head of triceps brachii
- Antagonists: Supraspinatus, anterior deltoid.
- Pelvic Upward Rotation: Latissmus dorsi contraction.
Muscle Actions by Planes - Adduction (180-0 degrees)
- Proximal Attachments on Scapula: Rhomboids combine with downward rotation and retraction.
- Secondary Movers (Synegists): Levator scapula, pectoralis minor, latissimus dorsi(60-30), lower trapezius(30-0)
- Stabilizing Synergists: Middle trapezius,
- Antagonist Muscles: Upper trapezius and serratus anterior
- The Primary Internal Rotators: Latissimus dorsi, pectoralis major, Subscapularis
Muscle Actions by Planes - Extension (180-0 Degrees)
- Primary Extensors: Latissimus dorsi, teres major, teres minor.
- Secondary Movers (Synergists): Posterior deltoid and long head of triceps brachii.
- Antagonists: Anterior deltoid, coracobrachialis, biceps brachii.
Summary Muscles Acting on the GH Joint
- Abduction: Posterior deltoids, middle/anterior deltoid, supraspinatus.
- Flexion: Anterior deltoid, coracobrachialis, long head of biceps.
- Adduction: Latissimus dorsi, teres major, pectoralis major.
- Extension: Latissimus dorsi, teres major, posterior deltoid, triceps brachii long head, and teres minor.
Summary Muscles Acting on the GH Joint (cont.)
- Internal Rotation: Subscapularis, pectoralis major, latissimus dorsi, teres major, anterior deltoid.
- External Rotation: Infraspinatus, teres minor, and posterior deltoid.
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Test your knowledge on the various joints of the shoulder complex and their functions. This quiz covers movements, types of joints, and anatomical connections within the shoulder girdle. Perfect for students studying anatomy or kinesiology.
