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Distal interphalangeal joint of hand

The distal interphalangeal (DIP) joint of the hand is the articulation between the head of the middle phalanx and the base of the distal phalanx in each finger (index to little finger). It is a synovial hinge-type joint, permitting mainly flexion and extension, with minimal lateral movement.

The DIP joints play a critical role in fine finger control, grip strength, and precision movements such as typing or pinching. Each joint is stabilized by a fibrous capsule, strong collateral ligaments, a palmar plate, and the surrounding tendinous apparatus (flexor and extensor tendons).

The thumb lacks a true DIP joint; instead, it has a single interphalangeal joint between its proximal and distal phalanges.

Synonyms

  • DIP joint of the finger

  • Terminal interphalangeal joint

  • Distal phalangeal articulation

Location and Structure

  • Articulation: Between the head of the middle phalanx and the base of the distal phalanx.

  • Joint type: Synovial hinge joint (ginglymus).

  • Capsule: Thin dorsally, reinforced on the sides and palmarly by dense fibrous tissue.

  • Cartilage: Both articulating surfaces are covered with hyaline cartilage, forming a smooth, congruent interface.

  • Range of motion: Approximately 60–80° of flexion; extension is minimal.

Relations

  • Dorsally: Terminal extensor tendon and thin joint capsule

  • Plantar (palmar) aspect: Flexor digitorum profundus tendon and volar plate

  • Laterally: Collateral ligaments and skin folds of the finger

  • Proximally: Middle phalanx

  • Distally: Distal phalanx and nail bed region

Ligamentous Attachments

  • Capsule: Surrounds the joint completely; thin dorsally, thicker on the sides and palmar aspect.

  • Collateral ligaments: Strong bands extending from the lateral aspects of the middle phalanx head to the distal phalanx base, resisting side-to-side motion.

  • Palmar (volar) plate: Fibrocartilaginous structure that prevents hyperextension and provides smooth gliding for the flexor tendon.

  • Extensor tendon expansion: Inserts dorsally into the base of the distal phalanx, facilitating finger extension.

Function

  • Flexion and extension: Allows distal finger bending and straightening for gripping, pinching, and fine manipulation.

  • Load transfer: Distributes axial forces during grasp and finger tip pressure.

  • Stability: Provides end-point support for the finger’s kinetic chain.

  • Precision control: Enables delicate and coordinated fingertip movements.

Clinical Significance

  • Osteoarthritis (Heberden’s nodes): Common degenerative condition causing bony enlargement and stiffness.

  • Mallet finger: Caused by extensor tendon avulsion at the DIP joint, leading to flexed fingertip deformity.

  • Fracture-dislocations: Involve avulsion of the dorsal or volar base of the distal phalanx.

  • Psoriatic arthritis: Often targets DIP joints with erosions and periostitis.

  • Rheumatoid arthritis: Less commonly affects DIP joints, but can in advanced disease.

  • Infection (septic arthritis): May follow penetrating trauma or paronychia.

  • Post-traumatic stiffness or capsulitis: Results from repetitive strain or scar contracture.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark).

    • Bone marrow: Bright due to fatty content.

    • Articular cartilage: Smooth thin layer of intermediate-to-low signal on both articulating surfaces.

    • Capsule and ligaments: Low signal intensity bands.

    • Pathology: Fracture or erosions appear as linear low-signal defects; bone marrow edema appears intermediate-to-bright.

  • T2-weighted images:

    • Cortex: Dark, low signal.

    • Bone marrow: Bright, slightly less than fat on T1.

    • Cartilage: Intermediate-to-bright signal; irregularities indicate degeneration or erosion.

    • Joint fluid: Bright hyperintense, outlining joint margins.

    • Pathology: Bone marrow edema, synovitis, and effusions appear as bright hyperintense regions.

  • STIR:

    • Normal bone marrow: Intermediate-to-dark signal.

    • Pathology: Bright hyperintense areas indicating marrow edema, infection, or active inflammation.

    • Highly sensitive for early detection of trauma, osteomyelitis, or arthropathy.

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow and cartilage: Intermediate-to-dark signal.

    • Pathology: Bright hyperintense zones in bone, cartilage, or soft tissue (indicative of edema, capsulitis, or synovitis).

    • Excellent for visualizing tendon insertions, collateral ligament tears, and joint effusion.

  • T1 Fat-Sat Post-Contrast:

    • Normal joint: Mild homogeneous enhancement of synovial lining.

    • Arthritis: Diffuse synovial thickening with strong enhancement.

    • Infection or osteomyelitis: Patchy marrow and soft-tissue enhancement with cortical disruption.

    • Chronic degenerative disease: Minimal or peripheral enhancement with osteophytes and cartilage loss.

CT Appearance

Non-Contrast CT:

  • Cortex: High attenuation, sharply defined.

  • Trabecular bone: Fine honeycomb pattern.

  • Articular surface: Smooth and congruent; cartilage appears as thin low-density line.

  • Pathology:

    • Fractures: Cortical breaks or avulsion fragments.

    • Osteoarthritis: Joint space narrowing, sclerosis, and osteophyte formation.

    • Erosions: Subchondral defects in inflammatory arthritis.

    • Calcifications: Possible within capsule or tendons in chronic disease.

Post-Contrast CT (standard):

  • Joint capsule and synovium: Enhancing in inflammatory or infectious conditions.

  • Soft tissues: Show contrast uptake in cellulitis or synovitis.

  • Utility: Excellent for assessing bone detail, erosive arthropathy, joint congruity, and post-surgical healing.

MRI images

Distal interphalangeal joint of hand axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI images

Distal interphalangeal joint of hand coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT images

Distal interphalangeal joint of hand sag ct image

CT VRT image

Distal interphalangeal joint of hand of hand 3D VRT CT image -img-00000-00000