Kinesiology Lecture 6-The shoulder complex

What has the greatest mobility of any joint in the body?

The shoulder

The shoulder provides a functional connection between?

The trunk and upper extremity

Mobility-stability requirement necessitates?

Dynamic stability in the shoulder

What are the bones of the shoulder complex?

-Scapula

-Clavicle

-Humerus

What are the functional articulations of the shoulder complex?

-Scapulothoracic joint (ST)

-Sternoclavicular joint (SC)

-Acromioclavicular joint (AC)

-Glenohumeral joint (GH)

What functional articulation of the shoulder is not a true joint?

Scapulothoracic

What is the scapulothoracic joint?

Articulation of the scapula with the thorax

The scapula is attached by?

Acromion to the clavicle (The acromioclavicular joint)

How is the clavicle attached to the sternum?

Sternoclavicular joint

Scapulothoracic movements are inescapably associated with motions of the?

Sternoclavicular joint

Acromioclavicular joint

ST movements are interdependent with the motions of the SC and AC joints which means what?

Movement of one equals movement of the other

ST, AC, and SC joints are what type of kinematic chain?

Closed: can’t move arm without moving clavicle

Since ST, AC, and SC joints are in a closed kinematic chain, movement of the scapula on the thorax results in?

Movement at one or both of the AC/SC joints

During abduction (protraction) of the scapula what happens?

Scapula moves away from spinal cord

During adduction (retraction) of the scapula what happens?

Scapula moves towards spinal cord

Normally, as the scapula slides along the curved thorax during abduction, the scapula maintains contact with the thorax by?

Following the contour of the rib cage and to allow the glenoid fossa to face anteriorly

What is winging?

Abnormal position of the scapula where there is a posterior displacement along verteral border of

Scapular winging is due to damage with what nerve?

Long thoracic

Dynamic scapular winging happens with?

Movement

What is static scapular winging?

Always there, stationary, structural deformity of some kind

What is scapular tipping?

Normal, when scapula goes into elevation, shrugging shoulders, inferior angle tips posteriorly, superior border moves anteriorly

What maintains position of scapula against rib cage?

Serratus anterior

Scapular stability occurs through?

Acromioclavicular and sternoclavicular joints and muscles that attach to the scapula and thorax

Why does scapular stability occur through acromioclavicular and sternoclavicular joints and muscles that attach to the scapula and thorax?

Because scapulothoracic joint is not a true joint

Ultimate function of the scapular motion is to?

-Orient the glenoid for optimal contact with the maneuvering arm

-Add range to elevate arm

-Provide stable base for controlled rolling/sliding of the articular surface of the humeral head

What joint is the base of operation for the scapula because, via the interposed clavicle, it is the only bony attachment of the scapula to the rest of the body?

Sternoclavicular joint

Movement of the clavicle at the sternoclavicular joint produces what?

Movement of the scapula and vice versa because it acts as a closed kinematic chain

What type of joint is a sternoclavicular joint?

Synovial with a joint capsule, three major ligaments and a joint disc

What type of joint is a sternoclavicular joint?

Saddle joint

What are the articulating surfaces of the sternoclavicular joint?

The sternal end of the clavicle and at the notch formed by the manubrium of the sternum and the first costal cartilage

What acts as a pivot during sternoclavicular motions?

Fibrocartilage sternoclavicular disc interposed between the articular surfaces

How many degrees of freedom does the sternoclavicular joint have?

3: elevation/depression, protraction/retraction, and rotation

What happens with elevation and depression of the sternoclavicular joint?

The distal segment of the clavicle goes up and down (associated with elevation and depression of the scapula)

What happens with protraction and retraction of the sternoclavicular joint?

Lateral end of the clavicle moves anteriorly/posteriorly (protraction associated with abduction, retraction associated with adduction of the scapula)

What happens with rotation in the sternoclavicular joint?

Clavicle rotates posteriorly from neutral bringing the inferior surface of the clavicle to face anteriorly

The acromioclavicular joint joins?

The acromion process of the scapula to the clavicle

What type of joint is an acromioclavicular joint?

Plane synovial joint, reflecting the predominantly flat contour of the joint surfaces

The acromioclavicular joint is surrounded by?

A capsule that is directly reinforced by superior and inferior ligaments (acromioclavicular ligaments)

What is the primary function of the acromioclavicular joint?

Maintain relationship between clavicle and scapula (it is a closed kinematic chain)

-Optimizes the mobility and fit between the scapula and thorax

The motions of the AC joint are described by?

The movement of the scapula relative to the lateral end of the clavicle

How many degrees of freedom of motion does the AC joint have?

3

Motions at the AC joint are motions described by?

Where glenohumeral joint articulates

What are the primary motions of the AC joint?

Upward and downward rotation

What are the secondary motions of the AC joint?

Pivoting and twisting around lateral end of clavicle

Small movements in horizontal and sagittal planes

Upward rotation of the AC joint occurs?

As the scapula swings upwardly and outwardly relative to the lateral end of the clavicle (abduction or flexion, frontal plane motion)

Downward rotation of the AC joint does?

Returns the scapula back toward the anatomic position (associated with shoulder adduction or extension)

Upward and downward rotation of the AC joint allows for?

Frontal plane motion of the scapula

Horizontal plane adjustments at the AC joint?

Occur around a vertical axis (transverse plane) as the medial border of the scapula pivots away and towards the posterior surface of the thorax

Internal and external rotation of the glenoid fossa occurs on what plane?

Transverse plane

Sagittal plane adjustments of the AC joint occur?

Around a near medial-lateral (frontal) axis, as the inferior angle pivots away or towards the posterior surface of the thorax

AC joint dislocation can occur?

When falling and striking the tip of the shoulder abruptly against an unyielding surface

What type of joint is the glenohumeral joint?

Ball and socket

How many degrees of freedom does the glenohumeral joint have?

3

Any motions of the GH joint may affect the?

Scapula

Elevation of the upper extremity refers to?

The combination of scapular, clavicular, and humeral motion that occurs when the arm is either raised in flexion or abduction and all motions in between

The glenohumeral joint has lots of ROM but that decreases?

Stability

What is the coracoacromial arch in regards to the glenohumeral joint?

Ligaments above humeral head to protect it

What is the plane and axis for flexion and extension of the shoulder?

Sagittal plane and frontal axis

What is the end feel for flexion and extension of the shoulder?

Firm

What is the range of motion for flexion of the shoulder?

0-180

What is the range of motion of shoulder extension?

0-60

What is the plane and axis for shoulder abduction and adduction?

Frontal plane and sagittal axis

What is the end feel for shoulder abduction and shoulder adduction?

Firm for abduction

Soft for adduction

What is the range of motion of shoulder abduction?

0-180

What is the range of motion of shoulder adduction?

180-0

What is the plane and axis for shoulder internal and external rotation?

Transverse plane with longitudinal axis

What is the end feel for shoulder internal and external rotation?

Firm

What is the range of motion of shoulder internal rotation?

0-70

What is the range of motion of shoulder external rotation?

0-90

What is the plane and axis of shoulder horizontal adduction and abduction?

Transverse plane with longitudinal axis

What is the end feel for shoulder horizontal adduction?

Soft or firm depending

What is the end feel for shoulder horizontal abduction?

Firm

What is the ROM for shoulder horizontal adduction?

0-135

What is the ROM for shoulder horizontal abduction?

0-45

The humeral head on the glenoid fossa forms a convex on concave movement which causes roll and slide to happen?

In opposite directions

What are the prime movers of the GH joint for abduction?

Deltoid

Supraspinatus

Anterior deltoid plays a role in?

Shoulder flexion

What amount of deltoid/supraspinatus force causes abduction?

Small amount

In order to abduct or flex the shoulder, what rotator cuff muscles contribute?

Infraspinatus

Teres Minor

Subscapularis

The rotator cuff muscles have what force in a caudal (downward) direction on the head of the humerus?

Translatory or linear force

The action of the deltoid along with the combined action of the rotator cuff muscles forms what which causes perfect spinning of humeral head in glenoid fossa?

Force couple

While teres minor, infraspinatus, and subscapularis push the deltoid down, what pulls it up?

Deltoid and supraspinatus

The divergent pulls of the forces create what in a force couple?

Pure rotation

What is happening in a force couple?

Multiple muscles working together but act in different directions to produce same motion

What are the rotator cuff muscles?

Supraspinatus

Infraspinatus

Teres minor

Subscapularis

How does the rotator cuff contribute to dynamic stability?

By rotating and compressing the head of the humerus into the glenoid fossa

What laterally rotates the humerus so the greater tubercle does not hit the acromion during abduction?

Teres minor and infraspinatus

What is rhythm in terms of joints?

More than one joint working together to achieve greater movement than if one joint was by itself

What is the scapulohumeral rhythm?

The coordinated concomitant movement of he GH joint with the scapula to provide the smoothest and greatest ROM in humerus abduction and flexion

What two joints make up scapulohumeral rhythm?

Scapulothoracic

Glenohumeral

The scapulothoracic joint contributes to elevation of the humerus upwardly by rotating the glenoid fossa how many degrees from resting position?

60

The glenohumeral joint contributes to how many degrees of flexion?

120

The glenohumeral joint contributes to how many degrees of abduction?

90-120

The combination of scapular and humeral movement results in the range of elevation to how many degrees?

180

Beyond 30 degrees flexion, the scapula and humerus move at what ratio?

1:2

60:120

Full flexion or abduction of the shoulder involves how much scapular rotation and how much humeral flexion?

Around 60 degrees scapular rotation

120 degrees humeral flexion

What is the purpose of the scapulohumeral rhythm?

Distributes the motion between two joints to permit a large ROM with less compromise of stability than if same range at one joint

Scapulohumeral rhythm maintain the glenoid fossa in an optimal position to?

Receive the head of the humerus to increase joint congruency while decreasing shear forces

Scapulohumeral rhythm permits what to maintain good length-tension relationship, minimizing active insufficiency of GH muscles?

Muscles acting on the humerus

In scapulohumeral rhythm, flexion requires what to bring the glenoid fossa forward, protecting the humerus from dislocating if force were applied?

Simultaneous abduction (protraction)