Topics

Topic

design image
Midcarpal joint

The midcarpal joint is a complex synovial articulation located between the proximal and distal rows of carpal bones in the wrist. It contributes significantly to the range of motion and stability of the wrist, particularly in flexion, extension, and ulnar or radial deviation. It is not a single joint cavity but a series of interconnected articulations forming a functional unit that works with the radiocarpal joint to provide smooth hand movements.

The midcarpal joint allows approximately half of total wrist flexion and extension, as well as a large component of circumduction. Its integrity is essential for coordinated motion between the proximal and distal carpal rows.

Synonyms

  • Intercarpal joint

  • Central carpal articulation

  • Middle carpal joint complex

Articulating Surfaces

  • Proximal row: Scaphoid, lunate, triquetrum

  • Distal row: Trapezium, trapezoid, capitate, hamate

  • The joint surfaces are reciprocal and irregular, forming interlocking convex and concave facets that ensure stability during movement.

  • The articulation between the capitate and lunate is the key pivot point of wrist motion.

Type of Joint

  • Synovial plane joint with complex interlocking surfaces.

  • Functionally acts as a hinge-gliding joint, allowing flexion, extension, and limited rotation.

Capsule and Ligaments

  • Joint capsule: Encloses the midcarpal joint, thin and loose to allow movement but strengthened by ligaments.

  • Palmar intercarpal ligaments: Strongest on the volar side; connect distal and proximal carpal bones, especially capitate to scaphoid and triquetrum.

  • Dorsal intercarpal ligaments: Stabilize dorsal aspect; connect trapezium to scaphoid, and capitate to lunate and triquetrum.

  • Radial collateral ligament: From radial styloid to scaphoid and trapezium, resists ulnar deviation.

  • Ulnar collateral ligament: From ulnar styloid to triquetrum and pisiform, resists radial deviation.

Relations

  • Superiorly: Radiocarpal joint

  • Inferiorly: Carpometacarpal joints

  • Dorsally: Extensor tendons and retinaculum

  • Palmarly: Flexor tendons and carpal tunnel structures

  • Laterally: Radial styloid and scaphoid

  • Medially: Triquetrum and ulnar side of wrist capsule

Function

  • Flexion and extension: Works with radiocarpal joint to produce smooth wrist flexion and extension.

  • Radial and ulnar deviation: Major contributor to side-to-side wrist movements.

  • Load transmission: Distributes axial load from hand to forearm.

  • Joint stability: Maintained through intercarpal ligaments and muscle-tendon coordination.

  • Kinematic coordination: Provides coupled motion; flexion of proximal row is accompanied by extension of distal row and vice versa.

Clinical Significance

  • Instability: Commonly associated with ligament injury (scapholunate or lunotriquetral).

  • Arthritis: Degenerative or post-traumatic osteoarthritis, especially after carpal fractures.

  • Carpal collapse: Seen in scapholunate dissociation or Kienböck disease (lunate avascular necrosis).

  • Synovitis: Inflammatory arthritis such as rheumatoid arthritis may affect this joint early.

  • Trauma: Fractures and dislocations alter joint congruity, leading to limited motion or pain.

  • Surgical relevance: Key consideration in partial wrist fusion and intercarpal arthrodesis procedures.

MRI Appearance

  • T1-weighted images:

    • Articular cartilage: Smooth, thin intermediate-to-low signal covering carpal bone surfaces.

    • Bone marrow: Bright signal due to fatty marrow in carpal bones.

    • Joint capsule: Thin low-signal outline between carpal rows.

    • Ligaments: Low-signal linear bands connecting carpal bones.

    • Pathology: Bone marrow edema appears intermediate-to-bright, fractures as low-signal lines.

  • T2-weighted images:

    • Cartilage: Intermediate-to-bright, clearly delineating joint spaces.

    • Fluid: Bright hyperintense signal outlining carpal articulations.

    • Bone marrow: Bright, though less intense than joint fluid.

    • Ligament tears: Focal discontinuity or bright signal replacing normal dark ligament band.

    • Degenerative changes: Cartilage thinning, subchondral cysts, and irregularity of joint margins.

  • STIR:

    • Normal bones: Intermediate-to-dark signal.

    • Pathology: Bright hyperintense marrow or pericapsular signal in edema, contusion, or synovitis.

    • Joint effusion: Bright signal expanding midcarpal recesses.

  • Proton Density Fat-Saturated (PD FS):

    • Cartilage and ligaments: Appear as low-to-intermediate signal.

    • Effusion, inflammation, or edema: Bright hyperintense signal in joint or pericapsular region.

    • Excellent for assessing ligament tears, synovitis, and early cartilage degeneration.

  • T1 Fat-Sat Post-Contrast:

    • Normal synovium: Mild homogeneous enhancement.

    • Inflammatory arthritis: Diffuse synovial enhancement with pericapsular thickening.

    • Post-traumatic changes: Patchy enhancement near fracture or ligament injury.

    • Arthrosis: Enhancing synovial pannus with subchondral marrow changes.

CT Appearance

Non-Contrast CT:

  • Bone cortex: High attenuation, sharply defined articular surfaces.

  • Joint spaces: Narrow low-density lines between carpal bones.

  • Pathology:

    • Identifies fractures, subluxations, osteophytes, or sclerosis.

    • Detects subtle malalignment in carpal instability patterns.

    • Excellent for preoperative planning in intercarpal fusion.

CT VRT 3D image

Midcarpal joint CT 3D VRT image -img-00000-00000

MRI image

Midcarpal joint coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Midcarpal joint CT coronal image