Muscle and Joint Interaction Flashcards
The entire UE is primarily innervated by what structure?
By the brachial plexus (ventral rami C5-T1 roots)
What order does the brachial plexus go in when it starts to bifurcate?
- Roots –> trunks –> Divisions –> Cords –> Branches
- Randy Travis Drinks Cold Beer
What roots are a part of the upper, middle, and lower trunks specifically?
- Upper: C5-6
- Middle: C7
- Lower: C8-T1
Where do the anterior and posterior divisions turn into the lateral, posterior, and middle cords?
At about the level of the clavicle
What roots does the SC joint get its innervation from?
C3-4 via the cervical plexus
What roots does the AC and GH joint get its innervation from?
C5-6 via the suprascapular and axillary nerves
What cord does the pec minor compress and why is this note worthy?
Pec minor compresses the posterior cord which gives off the radial and axillary nerve. The posterior cord also gives off the upper and lower subscapular nerves and the thoracodorsal nerve. Because of this, sometimes when the pec minor is too tight it can produce signs and symptoms that appear like cardiac issues (potential MI) in females.
The majority of muscles form the shoulder girdle are form 2 regions of the brachial plexus, what are they?
- The nerves from the posterior cord
- The nerves from the proximal segments of the brachial plexus
What nerves come off the posterior cord?
- Axillary
- Lower and Upper Subscapular
- Thoracodorsal
What nerves are apart of the proximal segment of the brachial plexus?
- Dorsal Scapular
- Long Thoracic
- Medial Pectoral
- Suprascapular
What innervates the Deltoid?
Axillary (C5-6 - Posterior cord)
What innervates the Teres Minor?
Axillary (C5-6 - Posterior cord)
What innervates the Latissimus Dorsi?
Thoracodorsal (C6-8 - Posterior cord)
What innervates the upper fibers of the Subscapularis?
Upper Subscapular (C5-6 - Posterior cord)
What innervates the lower fibers of the Subscapularis?
Lower Subscapular (C5-6 - Posterior cord)
What innervates the Teres Major?
Lower Subscapular (C5-6 - Posterior cord)
What innervates the Pectoralis Major?
Lateral Pectoral (C5-7 Lateral cord)
What innervates the sternocostal head of the Pectoralis Major?
Medial Pectoral (C8-T1 Medial cord)
What innervates the Pectoralis Minor?
Medial Pectoral (C8-T1 Medial cord)
What innervates the supraspinatus?
Suprascapular (C5-C6 Upper trunk)
What innervates the infraspinatus?
Suprascapular (C5-C6 Upper trunk)
What innervates the subclavius?
Subclavian (C5-C6 Upper trunk)
What innervates the rhomboids (major and minor)?
Dorsal Scapular (C5 - C5 nerve root)
What innervates the levator scapula?
Dorsal Scapular (C5 - C5 nerve root)
What innervates the serratus anterior?
Long thoracic (C5-C7 proximal to the trunks)
There are two main categories for shoulder muscles, what are they?
- Proximal stabilizers
- Distal Mobilizers
Where do the proximal stabilizers originate and insert?
- Originate on the spine, ribs, and cranium
- Insert on the scapula or clavicle
Where do the distal mobilizers originate and insert?
- Originate on the scapula or clavicle
- Insert on the humerus or forearm
Optimal function requires coordination interaction between what two things?
The proximal stabilizers and the distal mobilizers
What muscles elevate the scapula?
- Upper Trapezius (CN 11)
- Levator Scapulae (dorsal scapular)
- Rhomboids (major and minor) (dorsal scapular)
What muscles depress the scapula?
- Lower Trapezius (CN 11)
- Latissimus Dorsi (thoracodorsal)
- Pectoralis Minor (medial pectoral)
- Subclavius (subclavian)
What muscle protracts the scapula?
Serratus Anterior (long throacic)
What muscles retract the scapula?
- Middle Trapezius (CN 11)
- Rhomboids (major and minor) (dorsal scapular)
- Lower Trapezius (CN 11)
What muscles upwardly rotate the scapula?
- Serratus Anterior
- Upper Trapezius
- Lower Trapezius
What muscles downwardly rotate the scapula?
- Rhomboids
- Pectoralis Minor
What supports the posture of the shoulder girdle and the UE?
ST elevtors (Upper traps, levator, rhomboids)
When you lose muscular support in the shoulder, gravity will determine what?
The resting position of a usually depressed, protracted and excessively downwardly rotated scapula. Overtime this can damage the underlying structures
Depression can raise the thorax if the arm is …
Physically blocked and the scapula is stabilized or fixed
The Lat pulls the humerus in what direction?
Pulls the humerus inferiorly (indirect depression)
Motion at the ST joint occurs because of motions where?
At the SC and AC joints
The SC joint mainly preforms …
Elevation of the clavicle (roll/slide opposite)
The AC joint mainly preforms …
Slight anterior tilt and downward rotation
What are the arthokinematics of clavicle elevation and depression at the SC joint?
- Elevation: roll superior, slide inferior
- Depression: roll inferior, slide superior
What kind of scapular positions are predisposed to subacromial impingement?
- Slightly depressed, downwardly rotated, and protracted
- Scapula internally rotated and anteriorly tilted
The serratus anterior mainly helps with …
- Forward pushing and reaching
- Excellent leverage around the SC joints vertical axis
Does the pec minor have any ability to protract?
- Yes, but it is small
- It can limit retraction if tight
- Medial pectoral nerve
What exercise resembles protraction?
Push-up plus
Torque is muscle force times what?
internal moment arm (IMA)
What do the retractors of the scapula do?
- They are proximal stabilizers that anchor the scapula to the axial skeleton
- They are essential for pulling activities (rowing and climbing)
Does the SC joint mainly do protraction or retraction?
Protraction
Does the AC joint mainly do internal or external rotation?
Internal rotation
What are the arthrokinematics of protraction and retraction at the SC joint?
- Protraction: roll and slide anterior
- Retraction: roll and slide posterior
There are three groups for muscles that elevate the arm, what are they?
- Muscles that elevate the humerus at the GH joint
- Scapular muscles that control the upward rotation at the ST joint
- Rotator cuff muscles that control the dynamic stability and arthrokinematics of the GH joint
What are the 5 muscles that elevate the humerus at the glenohumeral joint?
- Anterior Deltoid (flexion and abduction)… axillary
- Middle Deltoid (abduction)… axillary
- Supraspinatus (abduction)… suprascapular
- Coracobrachialis (flexion)… musculocutaneous
- Biceps brachii (flexion)… musculocutaneous
Extreme upper fibers of the infraspinatus and the subscapularis perform slight _____ at the GH joint.
Abduction
What percentage of compression is found at 90 degrees of abduction?
80-90%
What percentage of compression is found at 90 degrees of abduction if you hold 2kg?
130%
What are the arthrokinematics of flexion and extension at the shoulder?
Flexion and extension is a spin of the humerus at the glenoid fossa
What is the axis of upward rotation of the ST joint?
Anterior - posterior at the scapula
What are the rolls of the upward rotators?
- Drive upward rotation and furnish rotational adjustments of the scapula (posterior tilt and external rotation - full abduction)
- Provide a stabile attachment for the more distal mobilizers (deltoid and the rotator cuff)
What muscle is the best leverage for upward rotation?
Serratus anterior
What do you typically see with trap muscle weakness?
- With full abduction the T spine extends to 10 - 15 degrees, if the traps are weak this range will change
- The pt will make adjustments in order to control the scapula movement
- Elevation is possible but difficult, they will compensate with excessive protraction instead of using the serratus anterior
- Abduction will be very difficult and will require use of the middle traps and retraction
Paralysis of the right serratus anterior is caused by and injury of what nerve?
Long thoracic nerve
What will you be able to see with serratus anterior weakness?
- The scapula will be anteriorly tilted and internally rotated
What is scapular dyskinesia?
- Describes any abnormal position or movement of the scapula
- Reduced upward rotation
- Excessive downward rotation, internal rotation, anterior tilt or elevation
- Accurate and reliable measurements are difficult to obtain
There are 3 patterns of the scapula, what are they associated with?
- Prominence of the inferomedial border of the scapula - Labral lesion
- Prominence of the entire medial border - Labral lesion
- Prominence of the superiomedial border - impingement and rotator cuff lesion
What muscles make up the rotator cuff?
- Infraspinatus
- Supraspinatus
- Teres Minor
- Subscapularis
What is the function of the RC muscles during elevation?
Regulation of dynamic joint stability and control of joint arthrokinematics
What helps with dynamic stability of the GH joint?
- A loose fit humeral head and glenoid fossa
- Extensive ROM in the GH joint
- A RC that compensates for natural laxity and natural tendency for instability
- Distal attachments of the RC that blend into the capsule before attaching to the proximal humerus
- Actively rotates the humeral head, compresses and stabilizes and is central in the fossa
- When the GH joint is activated it forms a protective cuff
Dynamic stability requires a healthy _____ and _____ system.
Neuromuscular and musculoskeletal
How many systems are integrated with proprioceptive sensory receptors in the GH periarticular tissue?
2
What are the arthrokinematics of abduction and adduction at the shoulder?
- Abduction: roll superior and slide inferior
- Adduction: roll inferior, slide superior
What muscle rolls the humeral head superiorly towards abduction while also compressing the joint for added stability?
Supraspinatus
What muscles exert a downward translation force on the humeral head and long head of the biceps to counteract the excessive superior translation caused by deltoid contraction during abduction?
- Subscapularis
- Infraspinatus
- Teres Minor
What muscles can externally rotate the humerus to increase the clearance of the greater tubercle and acromion during abduction?
- Infraspinatus
- Teres Minor
What muscles adduct and extend the shoulder?
- Posterior deltoid
- Latissimus dorsi
- Teres major
- Long head of the triceps brachii
- Sternocostal head of the pectroalis major
- Infraspinatus and teres minor assist
With the humerus stable, adduction and extension move the pelvis in what direction?
Upward (I.e. a pull up)
What muscles internally rotate the shoulder?
- Subscapularis
- Pectoralis major
- Latissimus dorsi
- Teres major
- Anterior deltoid
What muscles externally rotate the shoulder?
- Infraspinatus
- Teres minor
- Posterior deltoid
External rotation at the shoulder requires the scapula to be _____.
Stable
What movement has the lowest max effort torque but the highest velocity?
External rotation at the shoulder
What is the greatest moment of internal rotation?
30 degrees of elevation from the subscapularis
What is the least moment of internal rotation?
Anterior deltoid
Does internal rotation or external rotation have a greater mass?
Internal rotation
Does internal rotation or external rotation have a greater torque?
Internal rotation has a 40-70% greater torque
What are the arthrokinematics of external and internal rotation?
- External rotation: roll posterior and slide anterior
- Internal rotation: roll anterior and slide posterior
What muscle group order does peak torque go in from highest to lowest? (hint: concentric and eccentric are the same order)
- Highest: Extensors
- Adductors
- Flexors
- Abductors
- Internal rotators
- Lowest: External rotators
