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Carpal articular surface

The carpal articular surface refers to the smooth, cartilage-covered regions of the carpal bones that form articulations within the wrist complex. These surfaces allow for coordinated movement and force transmission between the radius, ulna, and carpal bones of the proximal and distal rows.

The carpal articular surfaces are lined with hyaline cartilage, providing a low-friction interface for movement and shock absorption. Collectively, they form part of the radiocarpal joint (between the radius and proximal carpal row) and the midcarpal joint (between proximal and distal carpal rows). Their integrity is essential for proper wrist function, stability, and smooth range of motion.

Synonyms

  • Wrist joint articular cartilage

  • Radiocarpal articular surface

  • Carpal cartilage plate

Location and Structure

  • Proximal carpal articular surface: Composed of the scaphoid, lunate, and triquetrum, articulating superiorly with the distal radius and articular disc of the distal radioulnar joint.

  • Distal carpal articular surface: Formed by the trapezium, trapezoid, capitate, and hamate, articulating with the bases of the metacarpals.

  • Cartilage covering: Smooth hyaline cartilage, typically 0.5–2 mm thick, ensuring frictionless motion.

  • Joint capsule: Encloses both radiocarpal and midcarpal joints, reinforced by palmar and dorsal ligaments.

  • Synovial membrane: Lines the non-articular portions, secreting synovial fluid for lubrication.

Relations

  • Proximally: Distal radius and articular disc of the distal radioulnar joint

  • Distally: Bases of metacarpal bones via the distal carpal row

  • Anteriorly (palmar): Flexor tendons and carpal tunnel structures

  • Posteriorly (dorsal): Extensor tendons and dorsal carpal ligaments

  • Laterally: Radial styloid process and scaphoid articulation

  • Medially: Triquetrum and pisiform region adjacent to ulnar collateral ligament

Ligamentous Attachments

  • Palmar radiocarpal ligaments: Connect radius to proximal carpal bones, stabilizing during extension

  • Dorsal radiocarpal ligaments: Prevent excessive flexion

  • Ulnar and radial collateral ligaments: Provide medial and lateral reinforcement

  • Intercarpal ligaments: Bind adjacent carpal bones, maintaining alignment and joint congruity

Composition and Histology

  • Articular cartilage: Hyaline type with organized collagen fibers providing durability and smoothness

  • Subchondral bone: Dense cortical layer supporting cartilage

  • Cartilage zones:

    • Superficial zone: Parallel collagen fibers resisting shear

    • Middle zone: Random collagen arrangement for shock absorption

    • Deep zone: Perpendicular fibers anchoring to subchondral bone

Function

  • Joint mobility: Enables wrist flexion, extension, abduction (radial deviation), and adduction (ulnar deviation)

  • Shock absorption: Cushions axial loads transmitted from hand to forearm

  • Load distribution: Spreads compressive forces evenly across carpal rows and radiocarpal interface

  • Smooth articulation: Minimizes friction between carpal bones during motion

  • Stability: Maintains congruency and alignment of carpal arches during movement

Clinical Significance

  • Osteoarthritis: Degenerative thinning or loss of cartilage causing joint space narrowing and sclerosis

  • Chondromalacia: Early softening of cartilage due to trauma or overuse

  • Post-traumatic arthritis: After fractures or ligamentous injury altering joint congruity

  • Inflammatory arthritis: Synovitis and cartilage erosion seen in rheumatoid disease

  • Avascular necrosis: Involvement of scaphoid or lunate leads to secondary cartilage collapse

  • Imaging importance: MRI and CT allow assessment of cartilage thickness, subchondral changes, and surface irregularities

MRI Appearance

  • T1-weighted images:

    • Cartilage: Intermediate-to-low signal, appearing smooth and uniform

    • Subchondral bone marrow: Bright signal (fatty marrow) underlying the articular surface

    • Cortical margins: Dark, sharply defined lines

    • Pathology: Chondral thinning or focal low-signal defects may indicate degeneration or early osteochondral injury

  • T2-weighted images:

    • Normal cartilage: Intermediate-to-bright signal, slightly darker than joint fluid

    • Subchondral bone: Low signal due to dense cortical composition

    • Joint fluid: Bright hyperintense outlining articular margins

    • Pathology: Cartilage fissures, erosions, or focal hyperintense defects correspond to chondral injury or early arthritis

  • STIR:

    • Cartilage: Intermediate-to-dark signal

    • Marrow edema or inflammation: Bright hyperintense signal in underlying bone indicating stress or trauma

    • Sensitive for detecting early bone marrow contusions, synovitis, and chondral edema

  • Proton Density Fat-Saturated (PD FS):

    • Cartilage: Intermediate-to-dark, with smooth homogeneous contour

    • Pathologic changes: Bright linear or focal hyperintensity within cartilage indicating softening or partial-thickness injury

    • Subchondral bone: Focal bright signal in edema or microfracture

  • T1 Fat-Sat Post-Contrast:

    • Normal cartilage: Minimal or no enhancement

    • Inflamed synovium or pannus (in arthritis): Shows strong contrast enhancement

    • Chronic degeneration: Peripheral rim enhancement with central low-signal fibrotic cartilage

CT Appearance

Non-Contrast CT:

  • Cartilage: Appears as a thin, low-density line between opposing bone surfaces

  • Subchondral bone: High attenuation, smooth cortical margins

  • Pathology:

    • Loss of joint space indicating cartilage thinning

    • Subchondral sclerosis, cysts, and marginal osteophytes in osteoarthritis

    • Flattening or step deformity from trauma or avascular necrosis

CT VRT 3D image

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MRI image

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MRI image

Carpal articular surface sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Carpal articular surface ct coronal image