movement sci: shoulder complex

What are the four articulations of the shoulder complex?

Glenohumeral (GH) Joint, Sternoclavicular (SC) Joint, Acromioclavicular (AC) Joint, Scapulothoracic (ST) Articulation

What type of joint is the Glenohumeral (GH) Joint?

A ball-and-socket joint

What movements does the GH joint allow?

Flexion, extension, abduction, adduction, internal rotation, and external rotation

What is the function of the Sternoclavicular (SC) Joint?

It allows the clavicle to move as the scapula moves and is important for transferring forces between the arm and trunk

What is the role of the Acromioclavicular (AC) Joint?

It allows adjustments between the scapula and clavicle and is important for full shoulder movement

What does the Scapulothoracic (ST) Articulation allow?

It allows the scapula to glide over the rib cage, positioning it during arm movement

What is the main concept regarding the shoulder complex?

The shoulder is a system where all four articulations must work together to create full shoulder range of motion (ROM)

What muscle actions depend on fiber orientation and joint position?

Muscle actions can vary, and different portions of one muscle can perform opposing movements

What are the primary functions of the Latissimus Dorsi?

Extension, adduction, and internal rotation

Which muscles are major shoulder force producers contributing to internal rotation?

Deltoid, pectoralis major, and latissimus dorsi

What is the role of the rotator cuff?

It stabilizes the GH joint and helps maintain appropriate humeral head positioning during movement

What does GH compression mean?

It refers to the muscles pressing the humeral head into the glenoid, preventing it from sliding away

What are the four muscles that make up the rotator cuff?

Supraspinatus, infraspinatus, teres minor, and subscapularis

What is the primary action of the supraspinatus?

Assists with abduction and produces GH joint compression

What is the main function of the infraspinatus?

External rotation and GH compression

What is the role of the teres minor?

External rotation, GH compression, and resisting anterior and superior translation

What is the primary action of the subscapularis?

Internal rotation and GH compression

What is a force couple in movement science?

It occurs when two or more muscles produce coordinated forces with different lines of pull to create or control movement

How do the deltoid and rotator cuff work together during shoulder abduction?

The deltoid elevates the arm while the rotator cuff compresses the humeral head into the glenoid for stability

What are the main movements of the scapula?

Elevation, depression, protraction, retraction, upward rotation, and downward rotation

What is scapulohumeral rhythm?

The relationship between GH motion and scapular motion during arm elevation

What is the ratio of GH movement to scapular movement during full shoulder elevation?

Approximately 2° GH movement for every 1° scapular movement

What is the function of the trapezius muscle?

It has three portions: elevation, retraction, and upward rotation of the scapula

What is scapular winging?

It occurs when the medial border of the scapula becomes prominent and lifts away from the rib cage, often due to serratus anterior dysfunction

What is the function of the serratus anterior?

Protraction, upward rotation, and posterior tilt of the scapula

What connects the clavicle to the sternum?

The sternoclavicular (SC) joint

What type of joint is the SC joint?

A saddle joint

What happens to the clavicle during movement in the frontal plane?

The clavicle rolls and glides in opposite directions relative to the concave sternum

What is the role of fascia and bursae in scapular movement?

They allow the scapula to glide smoothly along the rib cage and reduce friction during movement

What is the function of the teres major?

Extension, adduction, and internal rotation of the shoulder

What are the functions of the triceps brachii long head?

Shoulder extension and shoulder adduction

What is the primary action of the biceps brachii?

Shoulder flexion and some shoulder adduction

What is the function of the coracobrachialis?

Shoulder flexion and shoulder adduction

What is the primary movement of the clavicle during arm elevation?

The clavicle moves to accommodate scapular movement, including elevation and rotation

What are the two types of movements associated with the SC joint?

Elevation and depression of the clavicle

What is the role of the interclavicular ligament?

It limits excessive clavicular depression

What is the function of the costoclavicular ligament?

It limits excessive clavicular elevation

What type of joint is the acromioclavicular (AC) joint?

It connects the clavicle to the acromion of the scapula

What is the main purpose of the AC joint?

To allow adjustments between the clavicle and scapula during shoulder movement

What are the primary muscles involved in scapular elevation?

Upper trapezius and levator scapulae

What is scapular protraction?

Movement of the scapula laterally away from the spine

Which muscles are primarily responsible for scapular retraction?

Middle trapezius and rhomboids

What is the scapulohumeral rhythm?

The coordinated movement ratio of 2:1 between GH joint and scapular motion during shoulder elevation

What is the role of the rotator cuff during shoulder movement?

It stabilizes the humeral head and resists excessive translation

What happens to the humeral head during abduction at the GH joint?

The humeral head rolls superiorly and glides inferiorly

What is the significance of the convex-concave rule in the GH joint?

It indicates that roll and glide occur in opposite directions due to the joint's structure

What is the primary action of the deltoid muscle?

To generate force for humeral elevation

What is the function of the scapular upward rotation force couple?

To orient the glenoid upward during arm elevation

What is the role of the articular disc in the SC joint?

It improves joint congruency and helps resist separation

What muscles assist in scapular downward rotation?

Rhomboids and pectoralis minor

What is the function of the coracoclavicular ligament?

It limits superior-inferior and anterior-posterior displacement of the clavicle

What is the primary muscle responsible for scapular depression?

Lower trapezius and pectoralis minor

How does the SC joint accommodate scapular motion?

By allowing elevation, depression, protraction, retraction, and rotation

What is the role of the upper trapezius during shoulder elevation?

It assists in scapular upward rotation

What is the importance of the scapula during arm elevation?

It adjusts its position relative to the clavicle to maintain stability and function

What happens during scapular protraction?

The scapula moves laterally away from the spine, often during push-up movements

What is the function of the subclavius muscle?

It depresses the clavicle and helps stabilize the SC joint

What is the primary movement of the scapula during shoulder shrug?

Scapular elevation

What muscles assist with scapular stabilization during movements?

Rhomboids and lower trapezius

What is the significance of the AC joint in shoulder mechanics?

It allows for adjustments between the scapula and clavicle to maintain joint contact during movement