Shoulder joint, Sterno-clavicularjoint, Acromio-clavicular joint

Dr. Mohammed mahmoud Mosaed

Sternoclavicular Joint• Articulation: between the sternal end of the clavicle, the manubrium sterni, and

the first costal cartilage .

• Type: Synovial double-plane joint

• Capsule: This surrounds the joint and is attached to the margins of the articularsurfaces. Synovial membrane: This lines the capsule and is attached to the marginsof the cartilage covering the articular surfaces

• Ligaments: The capsule is reinforced by the strong sternoclavicular ligaments(anterior and posterior), interclavicular ligament

• Accessory ligament: The costoclavicular ligament is a strong ligament that runsfrom the junction of the first rib with the first costal cartilage to the inferior surfaceof the sternal end of the clavicle

• Articular disc: This flat fibrocartilaginous disc lies within the joint and divides thejoint's interior into two compartments. Its circumference is attached to the interiorof the capsule, but it is also strongly attached to the superior margin of thearticular surface of the clavicle above and to the first costal cartilage below.

• Nerve supply: The supraclavicular nerve and the nerve to the subclavius muscle

• Vascular supply by branches from the internal thoracic and suprascapular arteries.

Ligaments: The capsule is reinforced by the strong sternoclavicular ligaments (anterior and posterior), interclavicular ligamentAccessory ligament: The costoclavicular ligament is a strong ligament that runs from the junction of the first rib with the first costal cartilage to the inferior surface of the sternal end of the clavicle

Sternoclavicular joint

Movements and relations• Forward and backward movement of the

clavicle takes place in the medialcompartment. Elevation and depression ofthe clavicle take place in the lateralcompartment.

• Muscles Producing Movement• The forward movement of the clavicle is

produced by the serratus anterior muscle.• The backward movement is produced by the

trapezius and rhomboid muscles.• Elevation of the clavicle is produced by the

trapezius, sternocleidomastoid, levatorscapulae, and rhomboid muscles.

• Depression of the clavicle is produced bythe pectoralis minor and the subclaviusmuscles

Acromioclavicular Joint• Articulation: This occurs between the acromion of the scapula and the

lateral end of the clavicle .• Type: Synovial plane joint• Capsule: This surrounds the joint and is attached to the margins of the

articular surfaces• Ligaments: Superior and inferior acromioclavicular ligaments reinforce

the capsule;• Accessory ligament: The very strong coracoclavicular ligament extends

from the coracoid process to the undersurface of the clavicle. It hastrapezoid and conoid parts; It is largely responsible for suspending theweight of the scapula and the upper limb from the clavicle.

• Articular disc from the capsule, a wedge-shaped fibrocartilaginous discprojects into the joint cavity from above .

• Synovial membrane: This lines the capsule and is attached to the marginsof the cartilage covering the articular surfaces.

• Nerve supply: The suprascapular nerve• Vascular supply from the suprascapular and thoracoacromial arteries

• Ligaments: Superior and inferior acromioclavicular ligaments reinforcethe capsule;

• Accessory ligament: The very strong coracoclavicular ligament extendsfrom the coracoid process to the undersurface of the clavicle. It hastrapezoid and conoid parts; It is largely responsible for suspending theweight of the scapula and the upper limb from the clavicle.

Movements and relations

• A gliding movement takes place when the scapularotates or when the clavicle is elevated ordepressed.

• Important Relations

• Anteriorly: The deltoid muscle

• Posteriorly: The trapezius muscle

• Superiorly: The skin

Shoulder Joint

• Articulation: This occurs between the roundedhead of the humerus and the shallow, pear-shapedglenoid cavity of the scapula.

• The articular surfaces are covered by hyalinearticular cartilage, and the glenoid cavity isdeepened by the presence of a fibrocartilaginousrim called the glenoid labrum.

• Type: Synovial ball-and-socket joint

• Capsule: This surrounds the joint and isattached medially to the margin of theglenoid cavity outside the labrum;laterally it is attached to the anatomicneck of the humerus. The capsule is thinand lax, allowing a wide range ofmovement.

• It is strengthened by fibrous slips fromthe tendons of the subscapularis,supraspinatus, infraspinatus, and teresminor muscles (the rotator cuff muscles).

• Synovial membrane: This lines thecapsule and is attached to the margins ofthe cartilage covering the articularsurfaces . It forms a tubular sheatharound the tendon of the long head ofthe biceps brachii. It extends through theanterior wall of the capsule to form thesubscapularis bursa beneath thesubscapularis muscle.

Ligaments of shoulder joint

• Ligaments:• The glenohumeral ligaments

are three weak bands offibrous tissue that strengthenthe front of the capsule.

• The transverse humeralligament strengthens thecapsule and bridges the gapbetween the two tuberosities.

• The coracohumeral ligamentstrengthens the capsule aboveand stretches from the root ofthe coracoid process to thegreater tuberosity of thehumerus .

• Accessory ligaments: The coracoacromialligament extends between the coracoid processand the acromion. Its function is to protect thesuperior aspect of the joint.

• Nerve supply: The axillary and suprascapularnerves.

Movements of the shoulder joint• The shoulder joint has a wide range of movement

• The following movements are possible:

• Flexion: by the anterior fibers of the deltoid, pectoralis major(clavicular head), biceps, and coracobrachialis muscles.

• Extension: by the posterior fibers of the deltoid, latissimus dorsi, andteres major muscles.

• Abduction: by supraspinatus to 18⁰ and deltoid to 90⁰

• Adduction: by the pectoralis major, latissimus dorsi, teres major, and teres minor muscles.

• Lateral rotation: by the infraspinatus, the teres minor, and the posterior fibers of the deltoid muscle.

• Medial rotation: by the subscapularis, the latissimus dorsi, the teresmajor, and the anterior fibers of the deltoid muscle.

• Circumduction: This is a combination of the above movements

Important Relations

• Anteriorly: The subscapularis muscle and the axillaryvessels and brachial plexus.

• Posteriorly: The infraspinatus and teres minormuscles.

• Superiorly: The supraspinatus muscle, subacromialbursa, coracoacromial ligament, and deltoid muscle.

• Inferiorly: The long head of the triceps muscle, theaxillary nerve, and the posterior circumflex humeralvessels.

• The tendon of the long head of the biceps musclepasses through the joint and emerges beneath thetransverse ligament.

Stability of the Shoulder Joint

• The shallowness of the glenoid fossa of the scapulaand the lack of support provided by weak ligamentsmake this joint an unstable structure.

• Its strength almost entirely depends on the tone ofthe short muscles that bind the upper end of thehumerus to the scapula namely, the subscapularis infront, the supraspinatus above, and the infraspinatusand teres minor behind. The tendons of thesemuscles are fused to the underlying capsule of theshoulder joint. Together, these tendons form therotator cuff.

• The least supported part of the joint lies in theinferior location, where it is unprotected by muscles.