Elbow, radio-ulna, ponation & supination PDF

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Summary

Upper limb notes PS1001 - summary - exam...

Description

Elbow joint involves three separate articulations which have a common synovial cavity  Joints between the trochlear noth of the ulna and the trochlear of the humerus and between the head of the radius and the capitulum of the humerus are primarily involved with flexion and extension of the forearm, and, together are the principle articulations of the elbow joint 

The joint between the head of the radius and the radial notch of the ulna, the proximal radio-ulnar joint, is involved with pronation and supination of the forearm

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Articular surfaces of the bones of the forearm are covered with hyaline cartilage

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The synovial membrane originates from the edges of the articular cartilage and lines the radial fossa, the coronoid fossa, the olecranon fossa, the deep sryface of the joint capsule and the medial surface of the trochlea.

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Synovial membrane is separated from the fibrous membrane of the joint capsule by pads of fat in regions underlying the coronoid fossa, olecranon fossa and the radial fossa. Pads of fat accommodate related bony processes during extension and flexion of the elbow.

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Attachments of the bravhilis and triceps brachii muscles to the hoint capsule overlying these regions pull the attached fat pads out of the wat when the adjacent bony surfaces are moved into the fossae.

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The fibrous membrane of the hoint capsule overlies the synovial membrane, encloses the joint, and attaches to the medial epicondyle and the margins of the olecranon, coronoid, and radial fossae of the humerus. It also attaches onto the coronoid process and olecranon process of the ulna.

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On the lateral side, the free inferior margin of the joint capsule passes around the neck of the radius from an anterior attachment to the coronoid process of the ulna to a posterior attachment to the base of the olecranon

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The fibrous membrane of the joint capsule is thickened medially and laterally to form collateral ligaments, which support flexion and extension movements of the elbow joint.

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The exteral surface of the joint casule is reinforced laterally where it cuffs the head of the radius with a strong annular ligament of the radius. Although this ligament blends with the fibrous membrane of the jount capsule in most regions, they are separate posteriorly. The anular ligament also blends with the radial collateral ligament.

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The anular ligament of the radiys and related joint capsule allow the radial head to slide against the radial notch of the ulna and pivot on the capiulum during pronation and supination of the forearm.

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The deep surface of the fibrous membrane of the jont capsule and teh related anular ligament of the radius that articulate with the sides of the radil head are lined with cartilage.

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A pocket of synovial membrane protrudes from the inferior free margin of the joint capsule and facilitates rotation of the radial head during pronation and supination.

Distal radio-ulnar joint

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Occurs between the articular surface of the head of the ulna, with the ulnar notch on the end of the radius and with a fibrous articular disc, which separates the radioulnar joint from wrist joint. The triangular shaped articular disc is attached by its apex to a roughened depression on the ulna between the styloid process and articular ssurfave of the head, and by its base to the angular margin of the radius between the ulnar notch and the artucykar surface for the carpal bones The synovial membrane is attached to margins of the distal radio-ulnar joint and is covered on its external surface by a fibrous joint capsule The distal radio-ulnar joint allows the distal end of the radius to move anteromedially over the ulna

Interosseous membrane  It is a thin fibrous sheet that connects the medial and lateral borders of the radius and ulna respectively  Collagen fibres within the sheet pass predominantly inferiorly from the radius to the ulna  The interosseous membrane hs a free upper marhin which is situated inferior to radial tuberosity, and a small circle aperture in its distal third.  The interosseous membrane connects the radius and ulna without restricting pronation and supinaton an provide attachment for muscles in the anterior and posterior compartments.  The orientation of the fibres in the membrane is also consistent with its role in transferring forces from the radius to the ulna, therefore from the hand to the humerus Pronation and supination  Occurs entirely in the forearm and involve rotation of the radius at the elbow and movement of the distal end of the radius over the ulna  At the elbow, the superior articular surface of the radial head spins on the capitulum while, the at the same tiem, the articular surface on the side of the head slides against teh radial notch of the ulna and adjacent areas of the joint cosule and anular ligament of the radius.  At the distal radio-ulnar joint, the ulnar notch of the radius slides anteriorly over the convex surface of the head of the ulna  During these movements, the bones are held together by o The anular ligament of the radius at the proximal radio-ulnar joint o The interosseous membrane along the lengths of the radius and ulna, and o The articular disc at the distal radio-ulnar joint  Because the hand articulates predominantly with radius, the translocation of the distal end of the radius medially over the ulna moves the hand from the palmanterior (supination) to palm-posterior (pronation).  Two muscles supinate and two muscles pronate the hand Muscles that supinate the hand  Biceps brachii: largest of the four muscles that supinate and pronate the hand, is a powerful supinaor as well as flexor of the elbow joint. It its most effective as a supinator when the forearm is flexed

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Supinator: located in the posterior compartment of the forearm,. Has a broad origin from the supinator crest of the ulnar and the lateral epicondyle of the humerus and from ligaments associated with the elbow joint. Curves around the posterior surface and lateral surface of the upper third of the radius to attach to the shaft of the radius superior to the oblique line. The tendon of the biceps brachii muscle and the supinator muscle both become wrapped around the proximal end of the radius when the hand is pronated. When they contract, they unwrap from the bone, producing supination of the hand.

Muscles that pronate  Pronator teres and pronator quadratus are in the anterior compartment of the forearm  The pronator teres runs from the medial epicondyle of the humerus to the lateral shaft of the radius, approximately midway along the shaft  The pronator quadratus extends between the anterior surfaces of the distal ends of the radius and the ulna  When these muscles contract, they pull the distal end of the radius over the ulna resulting in pronation of the hand Anconeus  In addition to hinge-like flexion and extension at the elbow joint, some abduction of the distal end of the ulna also occurs and maintains the position of the palm of the hand over a central axis during pronation.  The muscle involved with this movement is the anconeus muscle, which is a triangular muscle in the posterior compartment of the forearm tht runs from the laterl epicondyle to the lateral surface of the proximal end of the ulna...