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Trochlea of phalanx

The trochlea of the phalanx refers to the pulley-shaped distal articular surface of a phalanx, most commonly seen at the head of the proximal and middle phalanges. It forms a critical component of the interphalangeal joints, allowing smooth hinge-like motion of the fingers and toes.

This structure is fundamental to digital biomechanics and is a key landmark in musculoskeletal anatomy, hand and foot imaging, and orthopedic evaluation.

Synonyms

  • Phalangeal trochlea

  • Trochlear surface of the phalanx

Location

  • Situated at the distal end of the proximal and middle phalanges

  • Forms the articular surface for the interphalangeal joints

  • Located between the medial and lateral condylar margins of the phalanx

  • Faces distally toward the base of the adjacent phalanx

  • Centered in the longitudinal axis of the digit

Anatomical components

  • Convex, pulley-shaped articular surface

  • Central groove:

    • Separates the medial and lateral articular facets

  • Articular cartilage covering

  • Subchondral bone beneath the cartilage

Relations

Proximally:

  • Body (shaft) of the phalanx

Distally:

  • Base of the adjacent phalanx

  • Articular cartilage interface

Medially:

  • Medial condylar margin of the phalanx

Laterally:

  • Lateral condylar margin of the phalanx

Dorsally:

  • Extensor tendon apparatus (in close proximity)

Ventrally (Palmarly/Plantarly):

  • Flexor tendon and volar plate

X-ray appearance

Plain radiographs (AP, lateral, oblique views):

  • Trochlea: Smooth, rounded articular contour at the distal phalanx end

  • Joint space: Uniform at the interphalangeal joint

  • Cortical margins: Sharp and continuous

  • Best visualized on: Lateral and oblique views

CT appearance

Non-contrast CT:

  • Trochlea: Well-defined convex articular surface

  • Subchondral bone: Uniform density beneath the articular cartilage

  • Cortical outline: Smooth and intact

  • Spatial detail: Excellent for assessing contour and symmetry

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal intensity

  • Subchondral marrow: High signal intensity

  • Articular contour: Clearly defined

T2-weighted images:

  • Articular cartilage: Intermediate-to-high signal

  • Subchondral bone: Low signal

  • Joint fluid: High signal outlining the trochlear surface

STIR:

  • Fat suppression: Uniform suppression of marrow fat

  • Trochlear margins: Clearly delineated

  • Joint fluid: Bright signal

Proton density fat-saturated (PD FS):

  • Articular cartilage: Well visualized with high contrast

  • Subchondral bone: Low signal

  • Joint space: Bright fluid signal

MRI image

Trochlea of phalanx mri anatomy labelled image-img-00000-00000

CT image

Trochlea of phalanx CT 1

CT image

Trochlea of phalanx CT