MSK S3 Shoulder Joint Flashcards
What type of joint is the shoulder joint
Synovial, ball and socket joint
Which two bones form the shoulder joint? Why is it said to be unstable?
Humerus and the glenoid fossa.
Said to be unstable because there is a 4:1 disproportion in area of surfaces.
What is put in pace to try to reduce the disproportion of the area of the surfaces?
Glenoid labrum. A fibrocartilage rim.
What other reasons cause the shoulder joint to be considered unstable?
The glenoid cavity/fossa is shallow
It allows multiplanar movements
The capsule is lax.
What is a joint capsule?
It is a fibrous sheath which encloses the structures of a joint.
How is stability of the shoulder joint achieved? What is most important?
Muscles of the rotator cuff (most important)
Glenoid labrum
Other muscles (deltoid, long head of biceps, triceps)
Ligaments
Capsule
What are the 3 intra-capsule ligaments of the shoulder otherwise known?
Gleno-humeral ligaments
Superior, Middle and inferior
What is the role of intracapsular ligaments of the shoulder joint?
They help to reinforce the joint anteriorly
What are the 3 extra-capsular ligaments of the shoulder joint?
Coracoacromial ligament
Coracohumeral ligament
Transverse humeral ligament
Where is the coracoacromial ligament found? What is it’s job?
It runs between the corocoid process of the scapula and the acromion of the scapula.
It prevents superior displacement of the humeral head. VERY STRONG
Where is the Coracohumeral ligament? what is it’s job?
Runs from the base of the coracoid process (on the scapula) to the anterior part of the greater tubercle on the humerus. It supports the superior part of the joint capsule.
Where is the transverse humeral ligament found? What is it’s job?
It spans the distance between the two tubercles of the humerus.
It holds to he tendon of the long head of biceps in place during shoulder movement.
What makes up the coracoacromial arch? What is the role of it? When is it clinically important?
Acromion Coracoid process Coracoacromial ligament Prevents up displacement of the humerus. Clinically important in the painful arc syndrome.
What gives the ‘cuff’ name to the rotator cuff muscles?
Their tendons blend in with each other to form a cuff, which fuses with the capsule and strengthens it.
What does the subacromial bursa separate?
The supraspinatus tendon from the coracoacromial ligament
What is the role of the synovial membrane in the shoulder joint?
It lines the capsule and the bone up to the edge of articulating surfaces
What are the 2 main bursa found in the shoulder joint?
The subscapular and subacromial
What is the role of the subacromial bursa?
It facilitates the movement of the supraspinatus tendin under the CAA snd the deltoid muscles over the SJ capsule and greater tubercle of the humerus.
When (at what degrees) does painful arc syndrome occur? AB or ADduction?
50-130 degrees
Name two causes of painful arc syndrome
Rotator cuff tendonitis (inflammation of the rotator cuff muscle tendons) or inflammation of the subacromial bursa.
Where is the subscapular bursa found? What is it’s role?
Located between the subscapularis tendon and the scapula. It facilitates, specifically, movement of the subscapularis muscle over the scapula.
What are the main blood supply to the shoulder joint?
Anterior and posterior circumflex arteries
Subscapular artery
What is a bursa?
A synovial fluid filled sac
What is the nerve supply to the shoulder joint?
Suprascapular nerve
Axillary nerve
Lateral pectoral nerves
Clinically how are dislocations of the shoulder joint described?
By where the humeral head lies in relation to the Infraglenoid tubercle.
What is an anterior dislocation usually caused by?
Excessive extension and lateral rotation of the humerus.
What nerve(s) are most likely to be damaged during anterior dislocation of the shoulder joint?
Axillary -can lead to paralysis of the deltoid muscles and loss of sensation over regimental badge area.
Radial nerve - bound in radial groove
