The humeroulnar joint (ulnohumeral or trochlear joint) is part of the

elbow-joint The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the med ...

. It is composed of two bones, the

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

and

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

, and is the junction between the trochlear notch of ulna and the

trochlea of humerus In the human arm, the humeral trochlea is the medial portion of the articular surface of the elbow joint which articulates with the trochlear notch on the ulna in the forearm. Structure In humans and apes it is trochleariform (or trochleiform), ...

. It is classified as a simple hinge-joint, which allows for movements of

flexion Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Ext ...

and circumduction. Owing to the obliquity of the trochlea of the humerus, this movement does not take place in the antero-posterior plane of the body of the humerus. When the forearm is extended and

supinated Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

, the axis of the arm and

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in ...

are not in the same line; the arm forms an

obtuse angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles a ...

with the forearm, known as the

carrying angle The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the media ...

. During flexion, however, the forearm and the hand tend to approach the middle line of the body, and thus enable the hand to be easily carried to the face. The accurate adaptation of the trochlea of the humerus, with its prominences and depressions, to the trochlear notch of the ulna, prevents any

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

movement. Flexion in the humeroulnar joint is produced by the action of the

biceps brachii The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join t ...

and

brachialis The brachialis (brachialis anticus), also known as the Teichmann muscle, is a muscle in the upper arm that flexes the elbow. It lies deeper than the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow ...

, assisted by the

brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way o ...

, with a tiny contribution from the muscles arising from the

medial epicondyle of the humerus The medial epicondyle of the humerus is an epicondyle of the humerus bone of the upper arm in humans. It is larger and more prominent than the lateral epicondyle and is directed slightly more posteriorly in the anatomical position. In birds, whe ...

. Extension in the humeroulnar joint is produced by the

triceps brachii The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of 3 parts: the medial, lateral, and long head. It is the muscle principally responsib ...

and

anconeus muscle The anconeus muscle (or anconaeus/anconæus) is a small muscle on the posterior aspect of the elbow joint. Some consider anconeus to be a continuation of the triceps brachii muscle. Some sources consider it to be part of the posterior compartment ...

, with a tiny contribution from the muscles arising from the

lateral epicondyle of the humerus The lateral epicondyle of the humerus is a large, tuberculated eminence, curved a little forward, and giving attachment to the radial collateral ligament of the elbow joint, and to a tendon common to the origin of the supinator and some of the ...

, such as the

extensor digitorum muscle The extensor digitorum muscle (also known as extensor digitorum communis) is a muscle of the posterior forearm present in humans and other animals. It extends the medial four digits of the hand. Extensor digitorum is innervated by the posterior int ...

Additional images

file:Gray331.png, Capsule of elbow-joint (distended) seen from front file:Gray332.png, Capsule of elbow-joint (distended) seen from back file:Gray329.png, Left elbow-joint showing anterior and ulnar collateral ligaments file:Gray330.png, Left elbow-joint showing posterior and radial collateral ligaments

References

Magee, David J. (2008) ''Orthopedic Physical Assessment'
p.361
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External links

* - "Joints of the Upper Extremity: Elbow joint" {{Authority control Joints Upper limb anatomy

Additional images

See also

References

External links