MRI Anatomy Flashcards · MSK

Elbow Anatomy

Learn to identify every labeled structure on a Elbow MRI, plane by plane.

Studying as a guest, so progress saves on this device only.

Elbow anatomy, structure by structure

Elbow MRI is a workhorse study for tendon, ligament, and cartilage problems, and reading it cleanly starts with knowing the normal anatomy across the three standard planes. This reference walks through every structure in our elbow flashcard deck on axial, coronal, and sagittal images, with a plain-language definition, how each structure looks on MRI, and the pathology you will actually run into at the scanner.

Bones and articulations

The bony framework of the elbow: the distal humerus meeting the radius and ulna. Coronal images compare the medial and lateral columns side to side, while sagittal images show the trochlea-ulna and capitellum-radius articulations front to back.

Humerus

The upper arm bone whose flared distal end forms the upper half of the elbow joint, articulating with both the radius and the ulna.

On MRI: Seen on all three planes; the distal shaft and metaphysis carry bright fatty marrow on T1 with a thin dark cortex. On coronal it forms the distal humerus, with its medial and lateral columns descending to the trochlea medially and the capitellum laterally.

Common pathology: Supracondylar and intercondylar fractures, marrow edema from stress or contusion, and osteomyelitis or marrow-replacing lesions show as low T1 and high fluid-sensitive signal.

Medial Epicondyle

The bony bump on the inner side of the distal humerus that anchors the common flexor-pronator origin and the ulnar collateral ligament.

On MRI: A short medial projection of the humerus, best located on coronal at the level of the joint line; marrow follows fat signal. The common flexor tendon arises from its anterior surface.

Common pathology: Medial epicondylitis (golfer's elbow), common flexor tendon tears, and avulsion injuries; in skeletally immature throwers the apophysis can avulse (Little League elbow).

Tip: On coronal it sits medial and slightly posterior; trace the common flexor tendon and ulnar collateral ligament down from it to confirm.

Lateral Epicondyle

The bony bump on the outer side of the distal humerus that anchors the common extensor origin and the radial collateral ligament.

On MRI: A lateral humeral projection on coronal at the joint line, with fatty marrow signal. The common extensor tendon, normally thin and dark, arises from it.

Common pathology: Lateral epicondylitis (tennis elbow) is the classic finding: thickening and increased signal at the common extensor origin, sometimes with an underlying radial collateral ligament tear.

Trochlea of Humerus

The spool-shaped medial articular surface of the distal humerus that articulates with the trochlear notch of the ulna.

On MRI: A rounded, cartilage-covered medial condyle on coronal, sitting just lateral to the medial epicondyle; the smooth low-signal cortex is capped by intermediate hyaline cartilage.

Common pathology: Osteochondral injury, marrow edema, and cartilage loss; fractures of the trochlea are uncommon but can be occult on radiographs and seen first on MRI.

Trochlear Notch

The C-shaped concavity of the proximal ulna that wraps around the trochlea of the humerus to form the hinge of the elbow.

On MRI: Seen as the curved articular surface of the proximal ulna cradling the trochlea on coronal and sagittal; the opposing cartilage surfaces follow intermediate signal.

Common pathology: Cartilage thinning and osteoarthritic spurring, and involvement in olecranon or coronoid process fractures that disrupt the notch.

Olecranon

The prominent proximal tip of the ulna that forms the bony point of the elbow and receives the triceps tendon insertion.

On MRI: The posterior bony projection of the proximal ulna; fatty marrow signal with the triceps tendon attaching to it. It seats into the olecranon fossa during extension.

Common pathology: Olecranon fractures, triceps insertional tendinopathy or avulsion, olecranon bursitis (fluid superficial to the bone), and stress changes in throwers.

Olecranon Fossa

The depression on the posterior distal humerus that receives the olecranon when the elbow is fully extended.

On MRI: A posterior hollow in the distal humerus on coronal, often containing a small amount of fat or fluid; its floor is thin bone separating it from the anterior coronoid fossa.

Common pathology: Loose bodies and posterior impingement collect here, and posteromedial osteophytes from valgus extension overload (throwers) can crowd the fossa.

Radius

The lateral forearm bone whose proximal head articulates with the capitellum of the humerus and the radial notch of the ulna.

On MRI: The lateral of the two forearm bones on coronal, with fatty marrow and thin cortex; its proximal end widens into the radial head and neck.

Common pathology: Radial head and neck fractures, proximal radioulnar instability, and marrow edema from impaction injuries.

Radial Head

The disc-shaped top of the radius that articulates with the capitellum of the humerus and rotates during pronation and supination.

On MRI: A rounded, cartilage-covered articular surface at the proximal radius on coronal and sagittal, facing the capitellum across the joint line.

Common pathology: Radial head fractures are among the most common elbow fractures and may be radiographically occult; MRI shows the fracture line plus marrow edema and a joint effusion or lipohemarthrosis.

Radial Neck

The narrowed segment of the proximal radius between the radial head above and the radial tuberosity below.

On MRI: The tapered bony segment just distal to the radial head on sagittal, with normal fatty marrow signal.

Common pathology: Radial neck fractures (often with the radial head), and marrow edema extending from a head fracture; angulation here affects forearm rotation.

Radial Tuberosity

The bony prominence on the medial aspect of the proximal radius that serves as the insertion site of the distal biceps brachii tendon.

On MRI: An eminence on the anteromedial proximal radius on sagittal and axial; the distal biceps tendon attaches to it. Best confirmed by following the biceps tendon to its insertion.

Common pathology: Distal biceps tendon avulsion off the tuberosity, and cortical irregularity or cysts from chronic tendon insertional change.

Tip: Follow the dark distal biceps tendon distally; the bone it dives toward on the anteromedial radius is the tuberosity.

Ulna

The medial forearm bone whose proximal end (olecranon and coronoid) forms the trochlear notch and the stable hinge of the elbow.

On MRI: The medial of the two forearm bones on coronal, with fatty marrow and thin cortex; proximally it broadens into the olecranon and trochlear notch.

Common pathology: Coronoid and olecranon fractures, stress injury, and involvement in complex fracture-dislocations such as the terrible triad.

Collateral ligaments

The paired ligament complexes that stabilize the elbow against valgus and varus stress. Both are best evaluated on coronal images, where they run vertically from the epicondyles to the forearm bones.

Ulnar Collateral Ligament

The medial ligament complex, whose anterior bundle runs from the medial epicondyle to the sublime tubercle of the ulna and is the primary restraint against valgus stress.

On MRI: A thin, taut low-signal band on coronal running from the undersurface of the medial epicondyle to the medial coronoid; the anterior bundle is the key segment to trace.

Common pathology: UCL tears are the signature injury of overhead throwing athletes; look for high signal, laxity, or distal detachment with the T-sign at the sublime tubercle on coronal arthrography.

Tip: This is the ligament reconstructed in Tommy John surgery; scrutinize the anterior bundle attachment on the sublime tubercle in any throwing athlete.

Radial Collateral Ligament

The lateral ligament arising from the lateral epicondyle that, with the lateral ulnar collateral ligament, resists varus stress and posterolateral rotatory instability.

On MRI: A thin low-signal band on coronal extending from the lateral epicondyle and blending with the annular ligament and the deep fibers of the common extensor origin.

Common pathology: Tears occur with lateral epicondylitis, elbow dislocation, and posterolateral rotatory instability; signal and discontinuity are assessed at the epicondylar origin.

Tendons and muscles

The major flexor and extensor units that cross the elbow. Tendons are normally thin and dark on all sequences; sagittal images are useful for following them to their bony attachments.

Biceps Brachii Muscle

The two-headed anterior arm muscle that flexes the elbow and supinates the forearm, tapering into the distal biceps tendon above the joint.

On MRI: A large anterior muscle belly on sagittal with normal striated muscle signal, narrowing into its tendon just proximal to the elbow.

Common pathology: Muscle strains and the retracted muscle belly seen after a distal biceps tendon rupture (the Popeye sign clinically).

Biceps Brachii Tendon

The distal tendon of the biceps that crosses the front of the elbow to insert on the radial tuberosity.

On MRI: A thin dark tendon coursing anteriorly and slightly laterally to the radial tuberosity; best followed on sequential axial slices and on sagittal to its insertion.

Common pathology: Distal biceps tendon partial or complete tear with retraction is the key diagnosis; fluid in the bicipitoradial bursa and an intact lacertus fibrosus affect the degree of retraction.

Tip: Track it slice by slice on axial from the muscle down to the radial tuberosity; a focal gap with surrounding fluid signals a tear.

Triceps Brachii Tendon

The common tendon of the three-headed posterior arm muscle that inserts on the olecranon and extends the elbow.

On MRI: A thick dark tendon on sagittal attaching to the posterior olecranon, best assessed in this plane for its full length and insertion.

Common pathology: Triceps tendinopathy and partial or complete avulsion off the olecranon (uncommon but easily missed); look for a fluid-filled gap and retraction on sagittal.

Frequently asked questions

What structures are seen on an elbow MRI?

A standard elbow MRI shows the distal humerus with its medial and lateral epicondyles, trochlea, capitellum, and olecranon fossa; the proximal radius (head, neck, tuberosity) and ulna (olecranon, coronoid, trochlear notch); the ulnar and radial collateral ligaments; and the major tendons and muscles including the biceps and triceps. This page labels each structure with its MRI appearance and the pathology techs commonly encounter.

Which plane is best for studying elbow anatomy?

All three planes work together. Coronal is the workhorse for the collateral ligaments and the bony columns (epicondyles, trochlea, capitellum, radial head). Axial is best for tracking tendons and muscles around the joint and confirming the biceps tendon course. Sagittal follows the biceps and triceps tendons to their attachments and shows the trochlea-ulna and capitellum-radius articulations.

What sequences are used for elbow MRI?

Most elbow protocols combine T1 for marrow and anatomy with fluid-sensitive fat-suppressed sequences (T2 or PD fat-sat, or STIR) to highlight edema, effusions, and tendon or ligament tears. Dedicated thin coronal images are angled for the collateral ligaments, and MR arthrography is sometimes added to evaluate the ulnar collateral ligament and cartilage.

How do you identify the ulnar collateral ligament on elbow MRI?

Use the coronal plane and trace the anterior bundle from the undersurface of the medial epicondyle to the sublime tubercle on the medial coronoid of the ulna. It should be a thin, taut, low-signal band. High signal, thickening, laxity, or a fluid undercut (the T-sign) at the sublime tubercle suggests a tear, which is common in overhead throwing athletes.

Do I need an account to use these elbow MRI flashcards?

No. The interactive flashcards and this full labeled reference are open to use, with no account required to start. Creating an account lets you save your progress across devices and track which packs you have mastered.

Tesla MR Institute

Training to become an MRI technologist?

These flashcards come from our MRI tech program — learn online and train at a clinical site near you, in 12 to 18 months.

Explore the program