Shoulder Joint, Rotator Cuff Muscles and Shoulder Joint Muscles Flashcards
The glenohumeral joint is what type of joint
Synovial ball and socket where the ball is the head of the humerus and the socket is the glenoid cavity of the scapula.
The rim of cartilage surrounding the socket is
The glenoid Labrum
What is the function of the glenoid labrum
To reduce the disproportion of the surfaces of the joint
What type of cartilage covers both of the articulating surfaces
Hyaline Cartilage
The head of the humerus is much larger than the glenoid fossa, what is the reason for this
Giving the joint inherant stability
The joint capsule
A fibrous sheath which encloses the structures of the joint. It extends from the anatomical neck of the humerus to the border of the glenoid fossa. The joint capsule is lax, creating greater mobility.
Subacromial Bursa
Located inferiorly to the deltoid and the acromion, and superiorly to the supraspinatus tendon and the joint capsule. It supports the deltoid and supraspinatus muscles. Inflammation of this muscle can result in several shoulder problems.
Subscapular bursa
Located between the subscapularis tendon and the scapula. It reduces wear and tear on the tendon during movement at the shoulder joint.
The majority of the shoulder joint ligaments are
Thickenings of the joint capsule
Glenohumeral Ligaments (superior, middle and inferior)
Consits of three bands, which run with the joint capsule from the glenoid fossa to the anatomical neck of the humerus. They act to stabilise the anterior aspect of the joint.
Coracohumeral ligament
Attaches the base of the coracoid process to the greater tubercle of the humerus. It supports the superior part of the joint capsule.
Transverse Humeral Ligament
This spans the distance between the two tubercles of the humerus. It holds the tendon of the long head of the biceps in the intertubercular groove.
Coracoacromial Ligament
Runs between the acromion and the coracoid process of the scapula forming the coraco-acrimial arch. The structure overlies the shoulder joint preventing superior displacement of the humeral head.
Common injury to damage the subacromial bursa
Subacromial bursitis
Arterial supply to the glenohumeral joint
Anterior and posterior circumflex humeral arteries and the subscapular artery.
Nerve supply to the glenohumeral joint
Axillary, suprascapular and lateral pectoral nerves.
Extension of the shoulder
Upper limb backwards in a sagittal plane. This is produced by the posterior deltoid, latissimus dorsi, long head of triceps brachii and teres major
Flexion of the shoulder
Upper limb forwards. Biceps brachii, pectoralis major, anterior deltoid and coracobrachilais
Abduction of the shoulder
Away from the midline. 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 – that is carried out by the trapezius and serratus anterior.
Adduction of the shoulder
Upper limb towards the body. Contraction of pectoralis major, latissimus dorsi and teres major.
Medial Rotation
Rotation towards the midline so that the thumb is pointing medially. Subscapularis, pectoralis major, latissimus dorsi, teres major and anterior deltoid.
Lateral Rotation
Rotation away from the midline so that the thumb is pointing laterally. Infraspinatus and teres minor.
Factors that contribute to the mobility of the shoulder joint
Type of joint (ball and socket), bony surfaces (shallow glenoid cavity and large humeral head), laxity of the joint capsule.
Factors that contribute to the stability of the shoulder joint
Rotator cuff muscles, glenoid labrum and the ligaments
Rotator cuff muscles
These muscles surround the shoulder joint, attaching to the tubercles of the humerus, whilst also fusing with the joint capsule. The resting tone of these muscles act to “pull” the humeral head into the glenoid cavity.
Glenoid Labrum
Fibrocartilaginous ridge surrounding the glenoid cavity. It deepens the cavity, reducing the risk of dislocation.
Dislocation of the Shoulder Joint (anterior dislocation)
Caused by excessive extension and lateral rotation of the humerus. The humeral head is forced anteriorly and inferiorly - into the weakest part of the joint capsule.
Rotator Cuff Tendonitis
Tendonitis refers to inflammation of the muscle tendons – usually due to overuse. Over time, this causes degenerative changes in the subacromial bursa, and the supraspinatus tendon. This increases friction between the structures of the joint.
The characteristic sign of rotator cuff tendonitis is the ‘painful arc’ – pain in the middle of abduction, where the affected area comes into contact with the acromion.
The nerves innervating the shoulder joint have what nerve roots
C5-6
The rotator cuff muscles orinigate and attach where
The scapula to the humeral head.
Movements of the glenohumeral joint caused by the rotator cuff muscles
Lateral rotation, medial rotation and abduction
Supraspinatus
Originates from the supraspinous fossa of the scapula and attaches to the greater tubercle of the humerus.
It is innervated by the suprascapular nerve.
Actions - Abducts the arm
Infraspinatus
Originates from the infraspinous fossa of the scapula and attaches to the greater tubercle of the humerus.
Innervation: Suprascapular nerve
Action: Laterally rotates the arm
Subscapularis
Originates from the subscapular fossa and attaches to the lesser tubercle of the humerus.
Innervation: Upper and lower subscapular nerves
Actions: medially rotates the arm
Teres Minor
Originates from the posterior surface of the scapula, adjacent to its lateral border. It attaches to the greater tubercle of the humerus.
Innervation: Axillary Nerve
Actions: Laterally Rotates the Arm
Deltoid
Originates from the scapula and the clavicle, attaches to the deltoid tuberosity on the lateral surface of the humerus.
Innervation: The axillary nerve
Actions: Anterior fibres flex the shoulder, posterior fibres extend the arm at the shoulder, middle fibres abduct the arm
Teres Major
Originates from the posterior surface of the inferior angle of the scapula. It attaches to the medial lip of the intertubercular groove of the humerus.
Innervation: Lower subscapular nerve
Actions: adducts at the shoulder and medially rotates the arm
Pectoralis Major
Fibres originate from the medial third of the clavicle, the sternum and the ribs.
It extends and medially rotates at the shoulder joint
Deltopectoral Triangle
Between the deltoid and pectoralis major muscle, subclavian vein is found here.
Nerve supply of serratus anterior
Long Thoracic Nerve
What clinical sign is seen on injury of the long thoracic nerve
Scapular Winging
When is the long thoracic nerve commonly injured
Breast surgery
Innervation of Trapezius Muscle
Accessory Nerve
Action of Latissimus Dorsi on the shoulder joint
Extension
Innervation of the Latissimus Dorsi Muscle
Thoracodorsal Nerve
Levator Scapulae
Originates from the transverse process of the C1-4 Vertebrae and attaches to the medial border of the scapula.
Innervation: Dorsal Scapular Nerve
Actions: Elevation of the scapula
Rhomboid Major
Originates from the spinous processes of T2-5 and attaches to the medial border of the scapula
Innervation: Dorsal Scapular Nerve
Actions: Retracts and rotates the scapula
Rhomboid Minor
Originates from the spinous processes of C7-T1 and attaches to the medial border of the scapula, at the level of the spine of the scapula.
Innervation: Dorsal Scapular Nerve
Actions: Retracts and rotates the scapula
