Elbow Joint And Radio Ulnar Joints

Elbow Joint The elbow joint, a hinge type of synovial joint, is located about 3 cm inferior to the epicondyles of the humerus.

Articulation of the Elbow Joint. Trochlea and capitulum of the humerus articulate with the trochlear notch of the ulna and the slightly concave superior aspect of the head of the radius, respectively; therefore, there are humero ulnar and humero radial articulations.

The articular surfaces, covered with hyaline cartilage, are most fully congruent (in contact) when the forearm is in a position midway between pronation and supination and is flexed to a right angle.

3 PALPABLE BONY POINTS AT THE BACK OF THE ELBOW

Joint Capsule of the Elbow Joint The fibrous layer of the joint capsule surrounds the elbow joint . It is attached at the margins of the articular surfaces of the capitulum and trochlea. Anteriorly and posteriorly it is carried superiorly, proximal to the coronoid and olecranon fossae. .

The synovial membrane lines the internal surface of the fibrous layer of the capsule and the intracapsular nonarticular parts of the humerus. It is also continuous inferiorly with the synovial membrane of the proximal radioulnar joint. The joint capsule is weak anteriorly and posteriorly but is strengthened on each side by collateral ligaments.

Ligaments of the Elbow Joint The collateral ligaments of the elbow joint are strong triangular bands that are the thickenings of the fibrous layer of the joint capsule . The lateral, fan-like radial collateral ligament extends from the lateral epicondyle of the humerus and blends distally with the annular ligament of the radius, which encircles and holds the head of the radius in the radial notch of the ulna.

A note about the annular ligament l Till

the 6 th year, the annular ligament is a ring like structure. Afterwards it narrows inferiorly and becomes cone shaped and extends to the neck of the radius. Hence the head of the radius in secured in the ring and slipping is prevented in adults.

The medial, triangular ulnar collateral ligament extends from the medial epicondyle of the humerus to the coronoid process and olecranon of the ulna and consists of three bands: (1)the anterior cord-like band is the strongest (2) the posterior fan-like band is the weakest, and (3)the slender oblique band deepens the socket for the trochlea of the humerus.

Cubital tunnel Flexor carpi ulnaris, medial epicondyle and medial collateral ligament of the elbow bound the cubital tunnel through which ulnar nerve passes and can be trapped leading to “cubital tunnel syndrome”.

Carrying angle

The long axis of the fully extended ulna makes an angle of 170°(approx) with the long axis of the humerus. This angle, called the carrying angle, is named for the way the forearm angles away from the body when something is carried, such as a pail of water.

The obliquity of the ulna and thus of the carrying angle is more pronounced (the angle is approximately 10° more acute) in women than in men. It is said to enable the swinging limbs to clear the wide female pelvis when walking. In the anatomical position, the elbow is against the waist. The carrying angle disappears when the forearm is in pronation and in flexion of the elbow too.

Movements and muscles causing them. Flexion and extension. The chief flexors of the elbow joint are the brachialis and biceps brachii (in that order) . The extensor is the triceps, especially the medial head.

Brachioradialis lIt

belongs to the extensor compartment of the forearm and is supplied by the radial nerve as it comes out of the spiral groove. It can flex the elbow and pronate and supinate the forearm.

Blood Supply of the Elbow Joint The arteries supplying the elbow joint are derived from the anastomosis around the elbow joint . Nerve Supply of the Elbow Joint The elbow joint is supplied by the musculocutaneous, radial, and ulnar nerves .

Bursae around the Elbow Joint Only some of the bursae around the elbow joint are clinically important. The three olecranon bursaeare the: Intratendinous olecranon bursa, which is sometimes present in the tendon of triceps brachii. Subtendinous olecranon bursa, which is located between the olecranon and the triceps tendon. Subcutaneous olecranon bursa, which is located in the subcutaneous connective tissue over the olecranon.

The subcutaneous olecranon bursa is exposed to injury during falls on the elbow and to infection from abrasions of the skin covering the olecranon.(student’s elbow)

Student’s(miner’s)elbow

Radio ulnar joints l Superior,

middle and inferior radio ulnar

joints. l Superior and inferior joints are pivot type. l Middle one is a fibrous joint. l Pronation and supination occur at the pivot. The radius moves during these movements.

Articulation of the Proximal Radioulnar Joint.

The head of the radius articulates with the radial notch of the ulna. The radial head is held in position by the annular ligament.

Middle radioulnar joint. Note the direction of fibers of interosseous membrane from radius to ulna!!!

Subluxation and Dislocation of Radial Head. Preschool children, particularly girls, are vulnerable to transient subluxation (incomplete temporary dislocation) of the head of the radius (also called nursemaid's elbow or pulled elbow). The history of these cases is typical. The child is suddenly lifted (jerked) by the upper limb while the forearm is pronated (e.g., lifting a child into a bus)

Distal Radioulnar Joint. The distal (inferior) radioulnar joint is a pivot type of synovial joint . The radius moves around the relatively fixed distal end of the ulna.

Articulation of the Distal Radioulnar Joint The rounded head of the ulna articulates with the ulnar notch on the medial side of the distal end of the radius. A fibrocartilaginous articular disc of the distal radioulnar joint (sometimes referred to by clinicians as the triangular ligament) binds the ends of the ulna and radius together and is the main uniting structure of the joint .

The articular disc separates the cavity of the distal radioulnar joint from the cavity of the wrist joint. It also prevents ulna in participating in the wrist joint.

Movements and muscles producing. lPronation–

pronator teres, pronator quadratus, brachioradialis. lSupination--- Supinator(when power is not required), biceps (when power is required)