Shoulder Joint Flashcards
What is the shoulder joint also known as?
The glenohumeral joint
What kind of joint is the shoulder joint?
Ball and socket
What is the shoulder joint between?
The scapula and the humerus
What does the shoulder joint do?
It is the major joint connecting the upper limb to the trunk
How does the mobility of the shoulder joint compare to the rest of the body?
It is one of the most mobile joints in the human body
What is the compromise for the mobility of the shoulder joint?
Less stable
What is the shoulder joint formed by?
The articulation of the head of the humerus with the glenoid cavity of the scapula
What are the articulating surfaces of the shoulder joints covered with?
Hyaline cartilage
What gives rise to the shoulder joints inherent instability?
The head of the humerus is much larger than the glenoid fossa
How is the disproportion of the articulating surfaces of the shoulder joint reduced?
The glenoid fossa is deepened by a fibrocartilage rim, called the glenoid labrum
What is the joint capsule of the shoulder joint?
A fibrous sheath which encloses the structures of the joint
What does the joint capsule of the shoulder joint extend?
From the anatomical neck of the humerus to the border of the glenoid fossa
What is the result of the joint capsule of the shoulder being lax?
It permits greater mobility, particularly abduction
What does the synovial membrane of the shoulders joint capsule line?
The inner surface of the joint capsule
What does the synovial membrane of the shoulders joint capsule produce?
Synovial fluid
Why does the synovial membrane of the shoulders joint capsule produce synovial fluid?
To reduce friction between the articular surfaces
How is friction in the shoulder joint reduced?
By the presence of several synovial bursae
What is a bursa?
A synovial fluid filled sac
What do bursa act as?
Cushions between tendons and other joint structures
What are the clinically important bursa in the shoulder joint?
Subacromial
Subscapular
Where is the subacromial bursa located?
Inferiorly to the deltoid and acromion
Superiorly to the supraspinatus tendon and the joint capsule
What does the subacromial bursa do?
Supports the deltoid and supraspinatus muscles
What can inflammation in the subacromial bursa lead to?
Several shoulder problems
Where is the subscapular bursa located?
Between the subscapularis tendon and the scapula
What is the function of the subscapular bursa?
Reduces wear and tear on the tendon during movement at the shoulder joint
What is the purpose of the ligaments in the shoulder joint?
They play a key role in stabilising the bony structures
What are the majority of the ligaments in the shoulder?
Thickenings of the joint capsule
What are the ligaments of the shoulder joint?
Glenohumeral ligaments (superior, middle and inferior)
Coroacohumeral ligament
Transverse humeral ligament
Coracoacromial ligament
What does the glenohumeral ligament consist of?
Three bands
Where do the glenohumeral ligaments run?
With the joint capsule, from the glenoid fossa to the anatomical neck of the humerus
What do the glenohumeral ligaments act to do?
Stabilise the anterior aspect of the joint
What does the coracohumeral ligament attach?
The base of the coracoid process to the greater tubercle of the humerus
What does the coroacohumeral ligament act to do?
Support the superior part of the joint capsule
Where is the transverse humeral ligament?
It spans the distance between the two tubercles of the humerus
What does the transverse humeral ligament act to do?
Hold the tendon of the long head of the biceps in the intertubecular groove
How is the coracoacromial ligament unlike the other ligaments of the shoulder joint?
It is not a thickening of the joint capsule
Where does the coracoacromial ligament run?
Between the acromion and coracoid process of the scapula
What does the coracoacromial ligament form?
The coraco-acromial arch
What does the coraco-acromial arch overlie?
The shoulder joint
What is the purpose of the coraco-acromial arch?
It prevents superior displacement of the humeral head
What is the arterial supply to the shoulder joint via?
The anterior and posterior circumflex humeral arteries, and the suprascapular artery.
Branches from these arteries form an anastomotic network around the joint
How is the shoulder joint innervated?
By the axillary, suprascapular and lateral pectoral nerves
What are the nerves that supply the shoulder joint derived from?
Roots C5 and C6 of the brachial plexus
What is the result of the innervation of the shoulder joint being from the brachial plexus?
A upper brachial plexus injury will affect shoulder joint function
What is an upper brachial plexus injury called?
Erb’s palsy
What is the result of the shoulder being a ball-and-socket type joint?
A wide range of movement is permitted
What movements does the shoulder joint permit?
Extension (upper limb backward in sagittal plane)
Flexion (upper limb forwards in sagittal plane)
Abduction (upper limb away from midline in coronal plane)
Adduction (upper limb towards the midline in coronal plane)
Medial rotation (rotation towards the midline, so the thumb is pointing medially)
Lateral rotation (rotation away from the midline, so the thumb is pointing laterally)
What is extension at the shoulder joint produced by?
The posterior deltoid, latissimus dorsi and teres major
What is flexion at the shoulder joint produced by?
The biceps brachii (both heads), pectoralis major, anterior deltoid and coracobrachialis
How is abduction at the shoulder joint produced?
The first 0-15 degrees of abduction is produced by the supraspinatus
The middle fibres of the deltoid are responsible for the next 15-90 degrees
Past 90 degrees, the scapula needs to be rotated to achieve abduction, which is carried out by the trapezius and serratus anterior
What produces adduction at the shoulder joint?
Contraction of the pectoralis major, lattissimus dorsi and teres major
How is adduction at the shoulder joint produced?
By contraction of the pectoralis major, latissimus dorsi and teres major
How is medial rotation of the shoulder joint produced?
By contraction of the subscapularis, pectoralis major, latissimus dorsi, teres major and anterior deltoid
How is lateral rotation of the shoulder joint produced?
Contraction of the infraspinatus and teres minor
What factors contribute to the mobility of the shoulder joint?
Type of joint- ball and socket
Bony surfaces
Laxity of joint capsule
What bony surfaces contribute to the mobility of the shoulder joint?
Shallow glenoid cavity and large humeral head- there is a 1:4 disproportion in surfaces
What factors contribute to the stability of the shoulder joint?
Rotator cuff muscles
Glenoid labrum
Ligaments
What do the rotator cuff muscles do?
Surround the shoulder joint, attaching to the tubercles of the humerus, whilst also fusing with the joint capsule
How do the rotator cuff muscles act to stabilise the shoulder joint?
The resting tone of the muscles act to ‘pull’ the humeral head into the glenoid cavity
What is the glenoid labrum?
A fibrocartilaginous ridge surrounding the glenoid cavity
What does the glenoid labrum do?
Deepens the cavity, reducing the dislocation
What do the ligaments of the shoulder act to do?
Reinforce the joint capsule
Form the coraco-acromial arch
Clinically, what are dislocations at the shoulder described by?
Where the humeral head lies in relation to the infraglenoid tubercle
What are the most prevalent shoulder dislocations?
Anterior dislocations, although posterior dislocations can sometimes occur
What prevents superior movement of the humeral head?
The coraco-acromial arch
What is an anterior shoulder dislocation usually caused by?
Excessive extension and lateral rotation of the humerus
What happens when there is excessive extension and lateral rotation of the humerus?
The humeral head is forced anteriorly and inferiorly, into the weakest part of the joint capsule.
What is tearing of the joint capsule associated with?
An increased risk of future dislocations
What runs in close proximity to the shoulder joint?
The axillary nerve
What is the result of the axillary nerve running in close proximity to the shoulder joint?
It can be damaged in dislocation
What does injury to the axillary nerve cause?
Paralysis to the deltoid, and loss of sensation over the regimental badge area
Why can a dislocation stretch the radial nerve?
As it is tightly bound in the radial groove
What is the important role of the rotator cuff muscles?
Stabilising the glenohumeral joint
How common is injuries of the rotator cuff muscles?
Relatively common
Why is injury of the rotator cuff muscles relatively common?
Because they are often under heavy strain
What does tendonitis refer to?
Inflammation of the muscle tendons
What is tendonitis usually due to?
Overuse
What does rotator cuff tendonitis cause over time?
Degenerative changes in the subacromial bursa, and the supraspinatus tendon
What do the changes found in rotator cuff tendonitis lead to?
Increased fiction between the structures of the joint
What is the characteristic sign of rotator cuff tendonitis?
The ‘painful arc’
What is the painful arc?
Pain in the middle of abduction
What causes the painful arc?
When the affected area comes into contact with the acromion
