Upper Limb - Joint Overview

Upper Limb - Joint Overview

• The shoulder consists of five joints: three true joints and two false joints.
• The glenohumeral joint is primarily focused, with its head of the humerus being larger than the glenoid cavity. The glenoid labrum encircles the glenoid cavity, increasing its stability.
• The acromioclavicular joint connects the distal clavicle and the acromion of the scapula, featuring limited mobility but high stability due to ligaments like the acromioclavicular and coracoclavicular (trapezoid and conoid).
• The sternoclavicular joint, between the clavicle and sternum, serves as the sole connection to the thorax. An articular disk adds to its stability, coupled with ligaments like the interclavicular, anterior, and posterior sternoclavicular.

Glenohumeral Joint

• This joint is inherently unstable, but stability comes from the glenoid labrum, joint capsule, and ligaments.
• The glenohumeral ligaments provide significant stability, preventing dislocations, especially when the arm is raised.
• The joint has a joint cavity with synovial fluid and cartilage.

Subacromial Impingement

• This refers to the reduction in the subacromial space due to various factors like the shape of the acromion, osteoarthritis of the acromioclavicular joint and/or ossification at the acromial level.
• This leads to impingement of the supraspinatus tendon, causing inflammation and degeneration, potentially resulting in rotator cuff tears.

Scapulothoracic Joint

• This is a false joint, providing a sliding space that facilitates the sliding of the rotator cuff tendons.
• The space lies between the scapula and the associated muscles. Separated by the serratus anterior.

Rotator Cuff Muscles

• The supraspinatus, infraspinatus, teres minor, and subscapularis muscles are essential for stability and movement within the glenohumeral joint.
• Each has a unique role in actions like abduction, external, and internal rotation.
• The supraspinatus is crucial for initial abduction, while external rotations are handled by infraspinatus and the teres minor

Shoulder Muscles

• Muscles connecting the shoulder girdle, shoulder to the humerus, and directly to the humerus (without connection to the scapula) are also outlined in the notes.
• Muscles like the pectoralis minor, trapezius, and rhomboids are outlined in these notes.

Elbow Joint

• Functionally divided into true and radio-ulnar parts.
• The true elbow joint is between the capitellum and head of the radius, and the trochlea and the semilunar surface of the ulna.
• The radio-ulnar joint, between the proximal ulna and radius, enables pronation and supination.