upper extremity

Which of the following fat pads/stripes should be demonstrated radiographically in a lateral projection of the normal adult elbow?

1. Anterior fat pad 2. Supinator fat stripe

A lateral projection of the hand in extension is often recommended to evaluate

1. a foreign body. 2. soft tissue.

The scapular Y projection of the shoulder demonstrates

1. an oblique projection of the shoulder. 2. anterior or posterior dislocation.

With which of the following does the trapezium articulate?

First metacarpal

Which of the following projection(s) require(s) that the shoulder be placed in internal rotation?

Lateral humerus

The fifth metacarpal is located on which aspect of the hand?

Medial

Which of the following projections of the elbow should demonstrate the coronoid process free of superimposition and the olecranon process within the olecranon fossa?

Medial oblique

The coronoid process should be visualized in profile in which of the following positions?

Medial oblique elbow

Which of the following is an important consideration to avoid excessive metacarpophalangeal joint overlap in the oblique projection of the hand?

Oblique the hand no more than 45°

What process is best seen using a perpendicular CR with the elbow in acute flexion and with the posterior aspect of the humerus adjacent to the image receptor?

Olecranon

Which of the following projections or positions will best demonstrate subacromial or subcoracoid dislocation?

PA oblique scapular Y

There are three important fat pads associated with the elbow.

The anterior fat pad is located just anterior to the distal humerus. The posterior fat pad is located within the olecranon fossa at the distal posterior humerus. The supinator fat pad/stripe is located at the proximal radius just anterior to the head, neck, and tuberosity. The posterior fat pad is not visible radiographically in the normal elbow.

What portion of the humerus articulates with the ulna to help form the elbow joint?

Trochlea

Which of the following projections will best demonstrate the carpal scaphoid?

Ulnar flexion/deviation

The axial trauma lateral (Coyle)

With the patient seated at the end of the x-ray table, elbow flexed 80°, CR directed 45° laterally from the shoulder to the elbow joint

The axial trauma lateral (Coyle)

With the patient seated at the end of the x-ray table, elbow flexed 90°, CR directed 45° toward the shoulder to the elbow joint

Bankart lesion

a fracture of the anteroinferior portion of the rim of the glenoid fossa.

The distal radius presents

a styloid process laterally; the ulnar notch is located medially, helping to form the distal radioulnar articulation. The distal surface of the radius (carpal articular surface) is smooth for accommodating the scaphoid and lunate to form the radiocarpal (wrist) joint.

The scapula's anterior, or costal, surface is that which is

adjacent to the ribs

The vertebral and axillary borders of the scapula are superimposed on the humeral shaft, and the resulting relationship between the glenoid fossa and humeral head will demonstrate

anterior or posterior dislocation

The greater and lesser tubercles

are prominences on the proximal humerus separated by the intertubercular (bicipital) groove.

Shoulder arthrography may be performed to evaluate

complete or incomplete rotator cuff tears

The ulna is the principal bone of the

elbow joint

rotator cuff tear

involves injury to one or more of the muscles participating in formation of that muscular structure. The supraspinatus, infraspinatus, subscapularis, and teres minor are the major muscles of the rotator cuff.

The lateral oblique elbow

projects the proximal radius and ulna free of superimposition.

The external rotation position

removes the humeral head from a large portion of the glenoid fossa and better demonstrates the greater tubercle.

A scapular Y projection is often performed to demonstrate

shoulder dislocation, but the affected arm is left to rest at the patient's side

The AP and scapular Y combination is the closest to

two views at right angles to each other.

the radius is the principal bone of the

wrist joint

A tear of the cuff can result in

subluxation; calcification can lead to shoulder immobilization.

With the patient seated at the end of the x-ray table, elbow flexed 90°, CR directed 45° toward the shoulder to the elbow joint, which of the following structures will be demonstrated best?

Radial head

Radial flexion/deviation is used to better demonstrate

medial carpals.

Acromioclavicular joint separation is demonstrated

on erect AP images with and without the use of weights.

The first metacarpal,

on the lateral side of the hand, articulates with the most lateral carpal of the distal carpal row, the greater multangular/trapezium. This articulation forms a rather unique and very versatile saddle joint, named for the shape of its articulating surfaces.

The coracoid process is located

on the scapula.

the exposure for the scapula is made during

quiet breathing to obliterate pulmonary vascular markings.

Lateral or medial dislocation of the shoulder is evaluated on

the AP projection

An AP projection of the elbow would demonstrate

partial overlap of the proximal radius and ulna

The first carpometacarpal joint is formed by the articulation of the base of the first metacarpal and the

trapezium

Adhesive capsulitis

"frozen shoulder," causes very diminished shoulder movement as a result of chronic joint inflammation.

Lateral epicondylitis

("tennis elbow") is a painful condition caused by prolonged rotary motion of the forearm.

bony structures into order (A-D) from lateral to medial.

(A) Trapezium (B) Trapezoid (C) Capitate (D) Hamate

Which of the following will separate the radial head, neck, and tuberosity from superimposition on the ulna?

Lateral oblique

shoulder arthritis demonstrated with

Routine radiographs

Shoulder arthrograms

are used to evaluate rotator cuff tear, glenoid labrum (a ring of fibrocartilaginous tissue around the glenoid fossa), and frozen shoulder.

With the patient seated at the end of the x-ray table, elbow flexed 80°, CR directed 45° laterally from the shoulder to the elbow joint, which of the following structures will be demonstrated best?

coronoid process

AP projection of the shoulder

there is superimposition of the humeral head and glenoid fossa. With the patient obliqued 45° toward the affected side, the glenohumeral joint is open, and the glenoid fossa is seen in profile. The patient's arm is abducted somewhat and placed in internal rotation.

transthoracic lateral projection

used to evaluate the glenohumeral joint and upper humerus when the patient is unable to abduct the arm.

To demonstrate the entire circumference of the radial head, exposure(s) must be made with the

1. epicondyles perpendicular to the cassette. 2. hand supinated as much as possible. 3. hand lateral and in internal rotation.

scapular Y

patient is positioned in a PA oblique position—an RAO or LAO, depending on which is the affected side. The midcoronal plane is adjusted approximately 60° to the IR, and the affected arm remains relaxed at the patient's side.

The AP projection of the humerus/shoulder

places the epicondyles parallel to the IR and the shoulder in external rotation, and demonstrates the greater tubercle in profile.

The lateral projection of the humerus

places the shoulder in extreme internal rotation with the epicondyles perpendicular to the IR and demonstrates the lesser tubercle in profile.

The scapula has no

sternal articulation

Which of the following is proximal to the carpal bones?

Radial styloid process

Hill-Sachs defect

a compression fracture of the posterolateral humeral head, usually associated with anterior dislocation of the shoulder joint. It can involve the cartilage of the humeral head, causing instability and predisposing the shoulder to subsequent dislocations.

Colles' fractures of the distal radius usually result from

a fall onto an outstretched hand with the arm extended.

Fractures of the radial head and neck frequently result from

a fall onto an outstretched hand with the elbow partially flexed

When the shoulder is placed in internal rotation

a greater portion of the glenoid fossa is superimposed by the humeral head and the lesser tubercle is visualized

All the following can be associated with the distal radius

a. styloid process. B. ulnar notch. C. radioulnar joint.

scapular Y projection

an oblique projection of the shoulder and is used to demonstrate anterior or posterior shoulder dislocation

scapular Y position is employed to demonstrate

anterior (subcoracoid) or posterior (subacromial) humeral dislocation. The humerus is normally superimposed on the scapula in this position; any deviation from this may indicate dislocation.

If routine elbow projections in extension are not possible

because of limited part movement, this position can be used to demonstrate the coronoid process and/or radial head. With the elbow flexed 90° and the CR directed to the elbow joint at an angle of 45° medially (ie, toward the shoulder), the joint space between the radial head and capitulum should be revealed. With the elbow flexed 80° and the CR directed to the elbow joint at an angle of 45° laterally (ie, from the shoulder toward the elbow), the elongated coronoid process will be visualized.

A medial oblique of the elbow would demonstrate

complete overlap of the proximal radius and ulna; this position is used to demonstrate the coronoid process in profile and the olecranon process within the olecranon fossa

The lateral oblique projection of the elbow

completely separates the proximal radius and ulna, projecting the radial head, neck, and tuberosity free of superimposition with the proximal ulna.

Although routine elbow projections may be essentially negative,

conditions may exist (such as an elevated fat pad) that seem to indicate the presence of a small fracture of the radial head. To demonstrate the entire circumference of the radial head, four exposures are made with the elbow flexed 90° and with the humeral epicondyles superimposed and perpendicular to the cassette: one with the hand supinated as much as possible, one with the hand lateral, one with the hand pronated, and one with the hand in internal rotation, thumb down. Each maneuver changes the position of the radial head, and a different surface is presented for inspection.

medial oblique position of the elbow demonstrates

considerable overlap of the proximal ulna, but should clearly demonstrate the coronoid process free of superimposition and the olecranon process within the olecranon fossa.

the proximal row of carpals

consists of, from lateral to medial, the scaphoid, the lunate/semilunar, the triangular/triquetrum, and the pisiform.

lateral oblique of the elbow

demonstrates the radial head free of superimposition with the ulna

transthoracic humerus or scapular Y would demonstrate

dislocation.

The bases of the metacarpals articulate with

each other and the distal row of carpals at the carpometacarpal joints.

wrist is composed of

eight carpal bones arranged in two rows (proximal and distal).

The distal row of carpals

from lateral to medial, consists of the trapezium/greater multiangular, the trapezoid/lesser multiangular, the capitate/os magnum (the largest carpal), and the hamate/unciform (which has a hooklike process, the hamulus).

The proximal radius

has a cylindrical head with a medial surface that participates in the proximal radioulnar joint; its superior surface articulates with the capitulum of the humerus.

To obtain an exact axial projection of the clavicle, place the patient

in a lordotic position and direct the central ray at right angles to the coronal plane of the clavicle

The fat pads of the elbow can be demonstrated only

in the lateral projection of the elbow (the posterior pad only in the presence of trauma/injury).

The coronoid process is best visualized

in the medial oblique position.

The carpal scaphoid

is a curved, boat-shaped, bone, and is therefore superimposed on itself ("self-superimposition") in a routine PA projection. Since the scaphoid is the most frequently fractured carpal, special projections have been developed to help overcome self-superimposition. Stecher (in 1937) recommended elevating the hand and wrist 20° and using a perpendicular CR directed to the scaphoid. Effective variations of this position include employing ulnar deviation and angling the CR 20° proximally (toward the elbow). The 20° tube angulation would be used in place of the elevated

The scapula

is a flat bone, shaped like an inverted triangle, with a costal surface that lies against the upper posterior rib cage. The scapula has a superior border, a medial (or vertebral) border, a lateral (or axillary) border, and an inferior angle, or apex. Its superior border presents a scapular notch projecting anteriorly just medial to the palpable coracoid process. The scapular spine divides the posterior surface into a supraspinatus fossa and infraspinatus fossa; the acromion process is the lateral extension of the scapular spine. The glenoid fossa is on the lateral aspect of the scapula and, with its articulation with the humeral head, forms the (ball and socket) shoulder joint.

The rotator cuff

is a musculotendinous structure that includes the supraspinatus, infraspinatus subscapularis, and teres minor muscles. The muscles function to stabilize the humeral head in all arm motions and, together with the deltoid, function to abduct and rotate the arm. Weakness of the rotator cuff can lead to impingement syndrome and/or tendonitis.

The coronoid process

is located on the proximal anterior ulna.

The exact axial projection

is performed by placing the patient in a lordotic position, leaning against the vertical grid device. This places the clavicle at right angles, or nearly so, to the plane of the IR. The central ray is directed to enter the inferior border of the clavicle, at right angles to its coronal plane. Other axial projections may include a prone position with a 25° to 30° caudal angle. However, none of these produce an exact axial projection of the clavicle.

The carpal scaphoid

is somewhat curved and consequently foreshortened radiographically in the PA position. To better separate it from the adjacent carpals, the ulnar flexion (ulnar deviation) maneuver is frequently employed. In addition to correcting foreshortening of the scaphoid, ulnar flexion/deviation opens the interspaces between adjacent lateral carpals.

A Colles' fracture

is usually caused by a fall onto an outstretched (extended) hand, to "brake" a fall. The wrist then suffers an impacted transverse fracture of the distal inch of the radius, with an accompanying chip fracture of the ulnar styloid process. Because of the hand position at the time of the fall, the fracture is usually displaced backward approximately 30°.

inferosuperior axial projection

may be used to evaluate the glenohumeral joint when the patient is able to abduct the arm

To evaluate the interphalangeal joints in the oblique and lateral positions, the fingers

must be supported parallel to the IR

Severe fractures often are accompanied by posterior dislocation of

the elbow joint.

To accurately position a lateral forearm

the elbow must form a 90° angle with the humeral epicondyles superimposed. The radius and ulna are superimposed only distally. Proximally, the coronoid process and radial head are superimposed, and the radial head faces anteriorly. Failure of the elbow to form a 90° angle or the hand to be lateral results in a less than satisfactory lateral projection of the forearm.

When the arm is placed in the AP position

the epicondyles are parallel to the plane of the cassette and the shoulder is placed in external rotation. In this position, an AP projection of the humerus, elbow, and forearm can be obtained; it places the greater tubercle of the humerus in profile.

With the arm in the anatomic position,

the fifth metacarpal and the ulna lie medially

To demonstrate the radius and ulna free of superimposition,

the forearm must be radiographed in the AP position, with the hand supinated. Pronation of the hand causes overlapping of the proximal radius and ulna. Two views, at right angles to each other, are generally required for each examination. Therefore, AP and lateral is the usual routine for an examination of the forearm.

The inferosuperior axial (nontrauma, Lawrence method) projection of the shoulder demonstrates

the glenohumeral joint and adjacent structures. The patient is supine with arm abducted 90°, and in external rotation. The (horizontal) CR is directed medially 25° to 30° through the axilla. The coracoid process and lesser tubercle are seen in profile

The bases of the proximal row of phalanges articulate with

the heads of the metacarpals to form the (condyloid) metacarpophalangeal joints, which permit flexion and extension, abduction and adduction, and circumduction.

The fingers must be supported parallel to the IR (eg, on a "finger sponge") in order that

the joint spaces parallel the x-ray beam. When the fingers are flexed or resting on the cassette, the relationship between the joint spaces and the IR changes, and the joints appear "closed."

When a patient's elbow needs to be examined in partial flexion

the lateral projection offers little difficulty

lateral projection of the elbow demonstrates

the olecranon process in profile.

When the elbow is placed in acute flexion with the posterior aspect of the humerus adjacent to the image receptor and a perpendicular CR is used

the olecranon process of the ulna is seen in profile

The tubercles are prominences located at

the proximal humerus and are anatomically remote from the elbow joint.

In the AP projection of the elbow,

the proximal radius and ulna are partially superimposed.

The distal humerus articulates with

the proximal radius and ulna to form the elbow joint. Specifically, the semilunar/trochlear notch of the proximal ulna articulates with the trochlea of the distal medial humerus.

The capitulum is lateral to the trochlea and articulates with

the radial head

AP projection of the elbow

the radial head and ulna are normally somewhat superimposed

In the lateral position of the elbow

the radial head is partially superimposed on the coronoid process, facing anteriorly.

The distal humerus articulates with

the radius and ulna to form the elbow joint. The lateral aspect of the distal humerus presents a raised, smooth, rounded surface, the capitulum, that articulates with the superior surface of the radial head. The trochlea is on the medial aspect of the distal humerus and articulates with the semilunar/trochlear notch of the ulna. Just proximal to the capitulum and trochlea are the lateral and medial epicondyles; the medial is more prominent and palpable.

With the patient in the AP position for the scapula

the scapula and upper thorax are normally superimposed. With the arm abducted, the elbow flexed, and the hand supinated, much of the scapula is drawn away from the ribs. The patient should not be rotated toward the affected side, as this causes superimposition of ribs on the scapula.

In the medial oblique position of the elbow

there is even greater superimposition.

If routine elbow projections in extension are not possible because of limited part movement

these positions can be used to demonstrate the coronoid process and/or radial head. With the elbow flexed 90° and the CR directed to the elbow joint at an angle of 45° medially (i.e., toward the shoulder), the joint space between the radial head and capitulum should be revealed. With the elbow flexed 80° and the CR directed to the elbow joint at an angle of 45° laterally (i.e., from the shoulder toward the elbow), the elongated coronoid process will be visualized.

"scapular Y"

this refers to the characteristic Y formed by the clearly visible humerus, acromion, and coracoid. The patient is positioned in a PA oblique position, The MCP is adjusted to approximately 60° to the IR, and the affected arm is left relaxed at the patient's side. The scapular Y position is employed to demonstrate anterior or posterior humeral dislocation. The humerus is superimposed on the scapula in this position; any deviation from this may indicate dislocation and the acromion process is free of superimposition.

To demonstrate a profile view of the glenoid fossa, the patient is AP recumbent and obliqued 45°

toward the affected side.

With the elbow in partial flexion

two exposures are necessary. One is made with the forearm parallel to the IR (humerus elevated), which demonstrates the proximal forearm. The other is made with the humerus parallel to the IR (forearm elevated), which demonstrates the distal humerus. In both cases, the central ray is perpendicular if the degree of flexion is not too great, or angled slightly into the joint space with greater degrees of flexion.

Acromioclavicular joints

usually examined when separation or dislocation is suspected. They must be examined in the erect position, because in the recumbent position, a separation appears to reduce itself. Both AC joints are examined simultaneously for comparison, because separations may be minimal.

The AP projection of the shoulder

will give a general survey and show medial/lateral and inferior/superior joint relationships.

The lateral hand in extension,

with appropriate technique adjustment, is recommended to evaluate foreign body location in soft tissue. A small lead marker is frequently taped to the spot thought to be the point of entry. The physician then uses this external marker and the radiograph to determine the exact foreign body location. Extension of the hand in the presence of a fracture would cause additional and unnecessary pain, and possibly additional injury.

following structures into order (A-D) from medial to lateral.

(A) Vertebral border (B) Scapular notch (C) Coracoid process (D) Acromion process

The scapular Y position

(LAO or RAO) is employed to demonstrate anterior (subcoracoid) or posterior (subacromial) humeral dislocation. The humerus is normally superimposed on the scapula in this position; any deviation from this may indicate dislocation. Rotational views must be avoided in cases of suspected fracture.

Which of the following articulations participate in the formation of the elbow joint?

1. Between the humeral trochlea and the semilunar/trochlear notch 2. Between the capitulum and the radial head 3. The proximal radioulnar joint

Which of the following is (are) associated with a Colles' fracture?

1. Chip fracture of the ulnar styloid 2. Posterior or backward displacement

Which of the following criteria is (are) required for visualization of the greater tubercle in profile?

1. Epicondyles parallel to the IR 2. Arm in external rotation 3. Humerus in AP position

Which of the following may be used to evaluate the glenohumeral joint?

1. Scapular Y projection 2. Inferosuperior axial 3. Transthoracic lateral

Which of the following is (are) valid criteria for a lateral projection of the forearm?

1. The coronoid process and radial head should be superimposed. 2. The radial tuberosity should face anteriorly.

When examining a patient whose elbow is in partial flexion, how should an AP projection be obtained?

1. With humerus parallel to IR, central ray perpendicular 2. With forearm parallel to IR, central ray perpendicular

The following procedure can be employed to better demonstrate the carpal scaphoid:

1. elevate hand and wrist 20°. 2. place wrist in ulnar deviation.

The medial oblique projection of the elbow demonstrates the

1. olecranon process within the olecranon fossa. 2. coronoid process free of superimposition.

For the AP projection of the scapula, the

1. patient's arm is abducted at right angles to the body. 2. patient's elbow is flexed with the hand supinated. 3. exposure is made during quiet breathing.

Muscles that contribute to the formation of the rotator cuff include the

1. subscapularis. 2. infraspinatus. 3. teres minor.

All of the following statements regarding the inferosuperior axial (nontrauma, Lawrence method) projection of the shoulder are true

1. the coracoid process and lesser tubercle are seen in profile 2. the arm is abducted about 90° from the body 3. the CR is directed medially 25° to 30° through the axilla.

In the lateral projection of the scapula, the

1. vertebral and axillary borders are superimposed. 2. patient may be examined in the erect position.

Which of the following tube angle and direction combinations is correct for an axial projection of the clavicle, with the patient in the PA position?

15° to 30° caudad

All the following can be associated with the distal ulna

A. head. B. radioulnar joint. C. styloid process.

All the following can be associated with the elbow joint

A. the capitulum. B. the trochlea. C. the epicondyles.

Which of the following projections is most likely to demonstrate the carpal pisiform free of superimposition?

AP (medial) oblique

Which of the following is most likely to be the correct routine for a radiographic examination of the forearm?

AP and lateral

Which of the following would be the best choice for a right-shoulder examination to rule out fracture?

AP and scapular Y

Which of the following will best demonstrate acromioclavicular separation?

AP erect, both shoulders

The scapula

presents two borders: the lateral or axillary border and the medial or vertebral border. It also presents three angles: the inferior angle, the superior angle, and the lateral angle. The processes of the scapula are the coracoid, the acromion, and the scapular spine. The scapula has a (supra) scapular notch, a supraspinatus fossa, and an infraspinatus fossa

lateral oblique (external rotation) projection of the elbow

removes the proximal radius from superimposition with the ulna and demonstrates its articulation with the ulna at the radial notch, the proximal radioulnar articulation.

The first carpometacarpal joint (thumb) is a

saddle joint, permitting flexion and extension, abduction and adduction, and circumduction; it is formed by the articulation of the base of the first metacarpal and the trapezium.

The oblique projection of the hand

should demonstrate minimal overlap of the third, fourth, and fifth metacarpals. Excessive overlap of these metacarpals is caused by obliquing the hand more than 45°. The use of a 45° foam wedge ensures that the fingers will be extended and parallel to the IR, thus permitting visualization of the interphalangeal joints and avoiding foreshortening of the phalanges.

Fracture of the distal radius is one of the most common

skeletal fractures.

A lateral projection of the scapula

superimposes its medial and lateral borders (vertebral and axillary, respectively). The coracoid and acromion processes should be readily identified separately (not superimposed) in the lateral projection. The erect position is probably the most comfortable position for a patient with scapula pain.

When a patient's elbow needs to be examined in partial flexion

the AP projection requires special attention. If the AP is made with a perpendicular central ray and the olecranon process resting on the tabletop, the articulating surfaces are obscured.

A plane passing through the epicondyles is parallel to

the IR (and perpendicular to the CR). To project the coracoid process with less self-superimposition, the CR must be angled cephalad between 15° and 45°. The amount of cephalad angulation depends on the degree of thoracic kyphosis; the greater the drgree of kyphosis, the greater the degree of cephalad angulation required. A 30° angle is used for the average patient.

For the lateral projection of the humerus

the arm is internally rotated, elbow somewhat flexed, with the back of the hand against the thigh and the epicondyles superimposed and perpendicular to the IR. The lateral projections of the humerus, elbow, and forearm all require that the epicondyles be perpendicular to the plane of the cassette.

The joints of the wrist include

the articulations between the carpals (intercarpal joints), which provide a gliding motion, and the radiocarpal joint (between the distal radius and scaphoid), which provides flexion and extension, abduction and adduction.

In the direct PA projection of the wrist

the carpal pisiform is superimposed on the carpal triquetrum. The AP oblique projection (medial surface adjacent to the IR) separates the pisiform and triquetrum and projects the pisiform as a separate structure. The pisiform is the smallest and most palpable carpal.

Clenching of the fist and ulnar flexion are maneuvers used to better demonstrate

the carpal scaphoid.

When the clavicle is examined in the PA recumbent position

the central ray must be directed 15° to 30° caudad to project most of the clavicle's length above the ribs. The direction of the central ray is reversed when examining the patient in the AP position.

"scapular Y" refers to

the characteristic Y formed by the humerus, acromion, and coracoid processes.

The medial oblique projection of the elbow demonstrates

the coronoid process in profile, as well as the ulnar olecranon process within the humeral olecranon fossa.

lateral projection of the scapula.

The axillary and vertebral borders are superimposed. The acromion and coracoid process are visualized; the coracoid process is partially superimposed on the axillary portion of the third rib.

elbow joint.

The distal humerus articulates with the radius and ulna to form a part of the elbow joint. The lateral aspect of the distal humerus presents a raised, smooth, rounded surface, the capitulum, that articulates with the superior surface of the radial head. The trochlea is on the medial aspect of the distal humerus and articulates with the semilunar notch of the ulna. All three articulations are enclosed in a common capsule to form the elbow joint proper.

The distal ulna

presents a head and styloid process and articulates with the distal radius to form the distal radioulnar joint. The ulna is slender distally but enlarges proximally and becomes the larger of the two bones of the forearm.

At its proximal end, the ulna

presents the olecranon process (posteriorly) and coronoid process (anteriorly) that are joined by a large articular cavity, the semilunar, or trochlear notch. The coronoid process fits into the humeral coronoid fossa during flexion, and the olecranon process fits into the humeral olecranon fossa during extension. Just distal and lateral to the semilunar/trochlear notch is the radial notch, which provides articulation for the radial head to form the proximal radioulnar articulation.