SHOULDER COMPLEX BONES, JOINTS, LIGAMENTS

SC Joint Articulation

Medial end of clavicle (convex) + Clavicular facet of sternum (concave) + Superior border of cartilage of 1st rib;

SC Joint Type

Saddle (Synovial, Diarthrodial);

SC Joint Movements

Elevation/Depression, Protraction/Retraction, Axial Rotation;

SC Joint Ligaments

Sternoclavicular, Interclavicular (between the clavicles), Costoclavicular (between ribs and clavicle);

SC Joint Planes & Axes

Sagittal (X axis): Protraction/Elevation; Frontal (Z axis): Retraction/Depression; Transverse (Y axis): Axial Rotation;

SC Joint Degrees of Freedom

3;

SC Joint Arthrokinematics: Elevation

Roll: Superior; Slide: Inferior;

SC Joint Arthrokinematics: Depression

Roll: Inferior; Slide: Superior;

SC Joint Arthrokinematics: Protraction

Roll: Anterior; Slide: Anterior;

SC Joint Arthrokinematics: Retraction

Roll: Posterior; Slide: Posterior;

SC Joint Arthrokinematics: Axial Rotation

Spin only (no roll/slide);

SC Joint Open Packed Position

Arm resting by side;

SC Joint Closed Packed Position

Arm maximally elevated;

SC Joint Capsular Pattern

Full elevation limited; pain at extreme ROM;

AC Joint Articulation

Lateral end of clavicle + Acromion of scapula;

AC Joint Type

Plane (Synovial, Diarthrodial) — both surfaces convex in shape;

AC Joint Movements

Upward/Downward Rotation, Internal/External Rotation, Anterior/Posterior Tilting;

AC Joint Ligaments

Acromioclavicular (superior/inferior fibers), Coracoacromial, Coracoclavicular (Conoid + Trapezoid);

AC Joint Superior AC Ligament

Limits inferior translation;

AC Joint Inferior AC Ligament

Limits superior translation;

AC Joint Conoid Ligament

Medial portion of coracoclavicular ligament; covers majority of posterior side; limits excessive superior translation;

AC Joint Trapezoid Ligament

Lateral portion of coracoclavicular ligament; limits scapula moving medially;

AC Joint Osteokinematic Planes

Sagittal (X axis): Anterior/Posterior Tilting; Frontal (Z axis): Upward/Downward Rotation; Transverse (Y axis): Internal/External Rotation;

AC Joint Degrees of Freedom

3;

AC Joint Upward Rotation Kinematics

Scapula swings upwardly and outwardly (associated with shoulder flexion/abduction);

AC Joint Downward Rotation Kinematics

Scapula returns toward anatomic position;

AC Joint Internal Rotation Kinematics

Medial border of scapula pivots away posteriorly (during scapulothoracic protraction);

AC Joint External Rotation Kinematics

Medial border returns toward anatomic position (during scapulothoracic retraction);

AC Joint Anterior Tilting Kinematics

Inferior angle of scapula pivots away from thorax (during scapulothoracic elevation);

AC Joint Posterior Tilting Kinematics

Inferior angle returns toward thorax (during scapulothoracic depression);

AC Joint Open Packed Position

Arm resting by side;

AC Joint Closed Packed Position

90 degrees of abduction;

AC Joint Capsular Pattern

Full elevation limited; pain at extreme ROM;

GH Joint Articulation

Head of the Humerus (convex, medial/posterior/superior) + Glenoid fossa (concave, lateral/anterior/superior);

GH Joint Type

Ball/and/Socket (Synovial, Diarthrodial);

GH Joint Movements

Flexion/Extension, Abduction/Adduction, Internal/External Rotation;

GH Joint Capsule

Surrounds the glenohumeral joint; loose and thin with surface area twice that of humeral head;

GH Joint Bursae

Limit excessive friction of structures (e.g., subacromial, subdeltoid);

GH Joint Foramen of Weitbrecht

Area of weakness in the capsule between superior and middle GH ligaments; common site of anterior dislocation;

GH Joint Axillary Pouch

Area of redundancy in inferior capsule; limits excessive motions of the shoulder; allows humeral head mobility during elevation;

GH Joint Coracohumeral Ligament

Limits excessive abduction and external rotation; prevents anterior/inferior translation; most affected ligament;

GH Joint Superior Glenohumeral Ligament

Taut when performing 0 to 45 degrees of abduction; prevents excessive abduction and external rotation;

GH Joint Middle Glenohumeral Ligament

Taut at 45 to 90 degrees of abduction; prevents excessive abduction and external rotation;

GH Joint Inferior Glenohumeral Ligament

Taut beyond 90 degrees of abduction; prevents excessive abduction and external rotation; main stabilizer of abducted shoulder;

GH Joint Osteokinematic Planes

Sagittal (X axis): Flexion/Extension; Frontal (Z axis): Abduction/Adduction; Transverse (Y axis): Internal/External Rotation;

GH Joint Degrees of Freedom

3;

GH Joint Arthrokinematics: Flexion

Humeral head spins on glenoid fossa; limited by posterior capsule;

GH Joint Arthrokinematics: Extension

Humeral head spins on glenoid fossa; limited by capsular ligaments;

GH Joint Arthrokinematics: Abduction

Roll: Superior; Slide: Inferior;

GH Joint Arthrokinematics: Adduction

Roll: Inferior; Slide: Superior;

GH Joint Arthrokinematics: Internal Rotation

Roll: Anterior; Slide: Posterior; limited by subscapularis;

GH Joint Arthrokinematics: External Rotation

Roll: Posterior; Slide: Anterior;

GH Joint Open Packed Position

55 to 70 degrees abduction + 30 degrees horizontal adduction + neutral rotation;

GH Joint Closed Packed Position

Maximum abduction and external rotation;

GH Joint Capsular Pattern

External Rotation > Abduction > Internal Rotation;

Scapulothoracic Joint Type

False joint (pseudo joint, functional joint) — connection between soft tissues, not a true synovial joint;

Scapulothoracic Joint Location

Anterior surface of the scapula + Posterolateral wall of the thorax;

Scapulothoracic Joint Functions

Provides mobility and stability; maintains length tension relationship for deltoids; provides shock absorption;

Scapulothoracic Joint Movements

Elevation Depression, Protraction Retraction, Upward Downward Rotation;

Scapulothoracic Joint SC Contribution: Elevation

30 to 45 degrees;

Scapulothoracic Joint SC Contribution: Depression

5 to 10 degrees;

Scapulothoracic Joint SC Contribution: Protraction/Retraction

15 degrees each;

Scapulothoracic Joint SC Contribution: Axial Rotation

40 degrees;

Scapulothoracic Joint AC Contribution: Elevation

20 degrees;

Scapulothoracic Joint AC Contribution: Upward Rotation

20 degrees;

Suprahumeral Joint Location

Between the head of the humerus and the arch formed by the neck of the scapula, the rigid coracohumeral ligament, and the coracoid process;

Suprahumeral Joint Function

Allows mobility of structures that pass through it; structural protection;

Scapulohumeral Rhythm Rule

After 30 degrees of abduction, there is a 2:1 ratio between glenohumeral and scapulothoracic joints;

Scapulohumeral Rhythm per 15 degrees

For every 15 degrees of abduction, 10 degrees occur at the glenohumeral joint and 5 degrees occur at the scapulothoracic joint;

Sternum Divisions

Divided into three parts: Manubrium sterni, Body of sternum, and Xiphoid process;

Manubrium Location

Upper part of sternum; lies opposite 3rd and 4th thoracic vertebrae;

Manubrium Articulations

Articulates with body of sternum at manubriosternal joint, clavicles, 1st costal cartilage, and upper part of 2nd costal cartilages;

Clavicular Facets

Articulates with the clavicle;

Costal Facets Location

Located on lateral edge of manubrium; provide bilateral attachment sites for first two ribs;

Jugular Notch

Located at superior aspect of manubrium between clavicular facets; a prominent concavity easily palpated;

Sternal Angle (Angle of Louis)

Formed by articulation of manubrium with body of sternum; transverse ridge lies at level of 2nd costal cartilage; opposite intervertebral disc between T4 and T5;

Xiphoid Process

Thin plate of cartilage that becomes ossified at proximal end during adult life; no ribs or costal cartilage attached to it;

Xiphisternal Joint

Lies opposite body of ninth thoracic vertebra;

Notches for 2nd to 7th Costal Cartilage

Serve as attachment for 2nd to 7th costal cartilages to form sternocostal joints;

Clavicle Shape

Long, slender bone lying horizontally across root of neck; medial two thirds convex forward, lateral one third concave forward;

Clavicle Anatomical Significance

Acts as strut holding arm away from trunk; transmits forces from upper limb to axial skeleton; provides muscle attachment;

Clavicle Orientation

Deviated about 20 degrees posterior to frontal plane;

Clavicle Medullary Cavity

Unlike typical long bones, clavicle usually has NO medullary cavity;

Clavicle Shaft

Curved with anterior surface generally convex medially and concave laterally;

Sternal End of Clavicle

Rounded prominent medial end; articulates with manubrium at sternoclavicular joint;

Costal Facet of Clavicle

Serves as attachment for first rib;

Costal Tuberosity

Serves as attachment for costoclavicular ligament;

Acromial End of Clavicle

Lateral end; articulates with scapula at acromioclavicular joint;

Acromial Facet

Articulates with scapula to form acromioclavicular joint;

Conoid Tubercle

Serves as attachment for conoid ligament (part of coracoclavicular ligament);

Trapezoid Line

Serves as attachment for trapezoid ligament (part of coracoclavicular ligament);

Groove for Subclavius Muscle

Serves as attachment for subclavius muscle;

Scapula Description

Large, flat triangular bone lying on posterolateral chest wall between 2nd to 7th ribs;

Scapula Orientation

Deviated 35 degrees anterior to frontal plane; glenoid fossa tilted approximately 5 degrees upward relative to vertebral border;

Superior Angle of Scapula

Superior medial aspect; provides attachment for levator scapulae muscle;

Inferior Angle of Scapula

Most inferior point where vertebral and axillary borders meet; determines scapular rotation; marks level of 7th rib and T7 spine;

Lateral Angle of Scapula

Truncated and broad; bears glenoid cavity which articulates with head of humerus at glenohumeral joint;

Medial/Vertebral Border

Between superior and inferior angles medially; attachment for levator scapulae, rhomboids, and serratus anterior;

Lateral/Axillary Border

Lateral side between glenoid fossa and inferior angle; separates attachments of subscapularis, teres minor, and teres major;

Superior Border of Scapula

Thin, sharp, shortest border; separated from coracoid process by suprascapular notch;