Shoulder joint Flashcards
What is another term for the shoulder joint?
Glenohumeral
What type of joint is it?
Ball and socket joint - sits between the humerus and scapula
The shoulder joint is one of the most mobile joints at the expense of…
Stability
The joint is formed by the articulation of the head of humerus with the…cavity
glenoid (fossa of the scapula)
Is it a synovial joint?
Yes
What cartilage covers the articulating surfaces?
Hyaline
Why does the joint have inherent instability?
The head of the humerus is much larger than the glenoid fossa - to reduce the disproportionate surfaces the fossa is deepened by a fibrocartilage rim = glenoid labrum
Describe the joint capsule
- Fibrous sheath that encloses the structures of the joint
- From anatomical neck of humerus to border of glenoid fossa
- capsule is lax to permit greater mobility
- synovial membrane lines inner surface of joint capsule
What does the synovial membrane produce?
Synovial fluid
What is the role of synovial bursae?
Reduce friction in joint
What is a bursae?
Fluid filled sac - acts a cushion between structures
What are the most clinically important bursae?
Subacromial
Subscapular
What ligaments are there?
1) Glenohumeral - superior, middle, inferior
- connect humerus to glenoid fossa
- main source of shoulder stability, holding it in place and preventing anterior dislocation
2) Coracohumeral - base of coracoid process to greater tubercle of humerus
- supports superior part of joint capsule
3) Coraco-clavicular - maintain alignment of clavicle in relation to scapula
4) Coracoacromial - forms the coracoacromial arch which prevents superior displacement of humeral head
5) Transverse humeral - holds tendon of long head of biceps in the intertubercular groove
What muscles are responsible for extension?
Posterior deltoid
Latissimus dorsi
Teres major
What muscles are responsible for flexion?
Pectoralis major
Anterior deltoid
Coracobrachialis
Biceps brachii weakly assist
What muscles are responsible for abduction?
First 15 degrees = supraspinatus
15-90 = middle fibres deltoid
past 90 = the scapula needs to be rotated - trapezius and serratus anterior
What muscles are responsible for adduction?
Pectoralis major
Latissimus dorsi
Teres major
What muscles are responsible for internal rotation?
Subscapularis Pectoralis major Latissimus dorsi Teres major Anterior deltoid
What muscles are responsible for external rotation?
Infraspinatus
Teres minor
What factors contribute to joint mobility?
Ball and socket joint
Shallow glenoid cavity and large humeral head
Inherent laxity of joint capsule
What factors contribute to stability?
Rotator cuff muscles
Glenoid labrum
Ligaments
Biceps tendon
What are the rotator cuff muscles?
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
What innervates teres minor?
Axillary nerve
What innervates Supraspinatous and infraspinatous?
Suprascapular nerve
What arteries supply the shoulder joint?
Anterior and posterior circumflex humeral arteries - branches of axillary artery
Branches of suprascapular artery (branch of thyrocervical trunk) also contribute
