MRI Anatomy Flashcards · MSK

Wrist Anatomy

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

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Wrist anatomy, structure by structure

Wrist MRI is one of the busiest small-part exams in musculoskeletal imaging, and reading it well starts with knowing the carpal anatomy cold. This reference walks through every structure in our wrist flashcard deck across the two workhorse planes (coronal and axial), with a plain-language definition, how each structure looks on MRI, and the pathology you will actually run into at the scanner.

Carpal bones

The eight small bones of the wrist, arranged in a proximal row (scaphoid, lunate, triquetrum, pisiform) and a distal row (trapezium, trapezoid, capitate, hamate). On the coronal you read them side to side across both rows; the axial shows them stacked through the carpal tunnel.

Scaphoid

The boat-shaped bone of the proximal carpal row on the thumb (radial) side, bridging the proximal and distal rows on the lateral wrist.

On MRI: Best traced on coronal images on the radial side, articulating with the distal radius proximally and the trapezium/trapezoid distally. Normal marrow is bright fatty signal on T1.

Common pathology: The most commonly fractured carpal bone. Because its blood supply enters distally, a proximal-pole fracture risks avascular necrosis and nonunion: watch for loss of normal T1 marrow signal.

Tip: Coronal fat-suppressed fluid-sensitive sequences (STIR or fat-sat T2) are the most sensitive for an occult scaphoid fracture when radiographs are negative.

Lunate

The crescent or moon-shaped bone in the center of the proximal carpal row, sitting directly on the distal radius.

On MRI: Found in the middle of the proximal row on coronal, between the scaphoid (radial) and the triquetrum (ulnar), articulating with the lunate fossa of the radius.

Common pathology: Site of Kienbock disease (avascular necrosis of the lunate): look for diffusely low T1 marrow signal, often associated with negative ulnar variance.

Triquetrum

The pyramid-shaped bone on the ulnar side of the proximal carpal row, sitting just beyond the lunate.

On MRI: Seen on the ulnar side of the proximal row on coronal images, distal to the triangular fibrocartilage complex (TFCC) and articulating with the pisiform on its palmar surface.

Common pathology: Second most commonly fractured carpal bone, usually a dorsal cortical avulsion or chip; ulnar-sided wrist pain may reflect associated TFCC injury.

Pisiform

A small pea-shaped sesamoid bone sitting on the palmar surface of the triquetrum within the flexor carpi ulnaris tendon.

On MRI: A rounded ossicle on the palmar/ulnar aspect of the wrist; on coronal it overlaps the triquetrum, so confirm its palmar position against the axial plane.

Common pathology: Pisotriquetral osteoarthritis and pisiform fractures cause focal ulnar-sided palmar pain; it is a landmark for Guyon canal and the ulnar nerve.

Trapezium

The most radial bone of the distal carpal row, articulating with the base of the thumb (first) metacarpal.

On MRI: Found at the radial edge of the distal row, distal to the scaphoid. Its saddle-shaped joint with the first metacarpal is best confirmed where the thumb base begins.

Common pathology: First carpometacarpal (basal thumb) osteoarthritis centers here, with cartilage loss, subchondral cysts, and marrow edema at the trapezium-metacarpal joint.

Trapezoid

The small wedge-shaped bone of the distal carpal row between the trapezium and the capitate, supporting the second metacarpal.

On MRI: The smallest distal-row bone, sitting between the trapezium (radial) and capitate (central) on coronal, distal to the scaphoid.

Common pathology: Isolated trapezoid injury is rare given its protected position; it is more often involved in high-energy carpal dislocations or perched fractures of the second metacarpal base.

Capitate

The largest carpal bone, sitting in the center of the wrist with a rounded head that fits into the concavity of the scaphoid and lunate.

On MRI: The central anchor of the carpal arch on both planes, between the trapezoid (radial) and hamate (ulnar), articulating proximally with the lunate.

Common pathology: Its rounded head can sustain avascular necrosis after trauma; the capitate is the central pivot disrupted in perilunate and lunate dislocations.

Hamate

The wedge-shaped bone on the ulnar side of the distal carpal row, articulating with the fourth and fifth metacarpals.

On MRI: Seen on the ulnar side of the distal row, just beyond the capitate, on both coronal and axial images.

Common pathology: Hamate body and hook fractures occur in racquet and club sports; the hook borders Guyon canal, so injury can produce ulnar nerve symptoms.

Hook of Hamate Bone

The palmar bony projection (hamulus) extending from the hamate that forms the ulnar wall of the carpal tunnel and the radial border of Guyon canal.

On MRI: A small hook-like spur projecting palmarly from the hamate, seen best on axial images where it juts into the soft tissues of the palm.

Common pathology: Hook of hamate fractures are classic in golf, baseball, and racquet sports and are easily missed on radiographs; axial fat-suppressed images show the fracture line and marrow edema.

Forearm bones

The radius and ulna form the proximal articular surface of the wrist. Their relative length (ulnar variance) and the ulnar styloid are key landmarks for ulnar-sided wrist pain.

Radius

The larger forearm bone on the thumb side whose distal end carries most of the load across the wrist joint.

On MRI: Forms the radial half of the proximal wrist articulation on coronal, with the scaphoid and lunate fossae receiving the proximal carpal row. Fatty marrow is bright on T1.

Common pathology: Distal radius fractures are among the most common upper-limb injuries; MRI is used for occult fractures and to assess associated TFCC and intercarpal ligament tears.

Ulna

The forearm bone on the little-finger side; its distal head sits adjacent to the wrist, separated from the carpus by the triangular fibrocartilage complex.

On MRI: Seen on the ulnar side of the distal forearm on coronal, with the TFCC bridging the gap between the ulnar head and the triquetrum.

Common pathology: Positive ulnar variance (a relatively long ulna) predisposes to ulnar impaction syndrome, with lunate and triquetral marrow edema and TFCC degeneration.

Ulnar Styloid Process

The bony projection at the back of the distal ulna that serves as an attachment for the triangular fibrocartilage complex.

On MRI: A small spur at the ulnar margin of the distal ulna on coronal images; the TFCC anchors at its base (the fovea).

Common pathology: Ulnar styloid fractures often accompany distal radius fractures; a nonunited styloid base fracture can destabilize the TFCC and distal radioulnar joint.

Carpal tunnel

The fibro-osseous channel on the palmar wrist, best evaluated in the axial plane where its boundaries and contents are seen in cross-section.

Carpal Tunnel

The palmar fibro-osseous canal bounded by the carpal bones behind and the flexor retinaculum (transverse carpal ligament) in front, transmitting the median nerve and the flexor tendons.

On MRI: Seen in cross-section on axial images: the arch of carpal bones forms the floor and walls, the flexor retinaculum stretches across the palmar surface, and the median nerve lies just deep to the retinaculum, superficial to the flexor tendons.

Common pathology: Carpal tunnel syndrome from median nerve compression: look for nerve flattening at the hamate level, nerve swelling at the pisiform level, increased T2 nerve signal, and palmar bowing of the flexor retinaculum.

Tip: Trace the median nerve on sequential axial slices; it is normally slightly brighter than the adjacent flexor tendons on fluid-sensitive sequences, which helps separate nerve from tendon.

Frequently asked questions

What structures are seen on a wrist MRI?

A standard wrist MRI shows the eight carpal bones (scaphoid, lunate, triquetrum, pisiform in the proximal row; trapezium, trapezoid, capitate, hamate in the distal row, plus the hook of the hamate), the distal radius and ulna with the ulnar styloid process, and the carpal tunnel with the median nerve and flexor tendons. This page labels each one with its MRI appearance across the coronal and axial planes.

Which plane is best for studying wrist anatomy?

The coronal plane is the best single view for the carpal bones, the proximal and distal rows, the intercarpal ligaments, and the triangular fibrocartilage complex. The axial plane is best for the carpal tunnel, the median nerve, the flexor and extensor tendons, and the hook of the hamate. Most wrist protocols read coronal and axial together, with sagittal added for carpal alignment.

Which carpal bone is most commonly fractured, and why does it matter on MRI?

The scaphoid is the most commonly fractured carpal bone. Its blood supply enters from the distal pole, so a proximal-pole fracture can cut off perfusion and lead to avascular necrosis and nonunion. On MRI, watch for loss of the normal bright T1 fatty marrow signal in the scaphoid; coronal fat-suppressed fluid-sensitive sequences are the most sensitive for an occult fracture when radiographs look normal.

How is the carpal tunnel and median nerve evaluated on MRI?

The carpal tunnel is read in the axial plane, where the carpal arch forms the floor and the flexor retinaculum stretches across the palmar surface. The median nerve lies just deep to the retinaculum, superficial to the flexor tendons. In carpal tunnel syndrome, look for nerve flattening at the hamate level, nerve swelling and increased T2 signal at the pisiform level, and palmar bowing of the flexor retinaculum.

Do I need an account to use these wrist 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.

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