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Interosseous border

The interosseous border is a sharp, elongated ridge found on certain long bones, most notably the radius, ulna, tibia, and fibula. It serves as the principal attachment site for the interosseous membrane, a fibrous sheet connecting paired bones of the forearm and leg. This border plays a critical role in maintaining alignment, stability, and force transmission between adjacent bones.

It is an important landmark in musculoskeletal anatomy, orthopedic imaging, trauma evaluation, and surgical planning.

Synonyms

  • Interosseous crest

  • Interosseous ridge

Location

  • Found on paired long bones

  • Radius and ulna:

    • Located along the medial border of the radius

    • Located along the lateral border of the ulna

  • Tibia and fibula:

    • Located along the lateral border of the tibia

    • Located along the medial border of the fibula

  • Extends longitudinally along the diaphysis

  • Oriented toward the adjacent paired bone

Anatomical components

  • Sharp bony ridge or crest

  • Continuous cortical thickening

  • Attachment site for the interosseous membrane

  • Contributes to the shape and contour of the diaphysis

Relations

Anteriorly:

  • Anterior muscle compartments

  • Anterior neurovascular structures (region dependent)

Posteriorly:

  • Posterior muscle compartments

Medially or laterally (depending on bone):

  • Interosseous membrane

  • Opposing paired bone

Superiorly and inferiorly:

  • Blends with metaphyseal bone near joints

Structures attached

  • Interosseous membrane of the forearm or leg

  • Occasional muscular fibers (e.g., deep flexors/extensors)

  • Periosteum continuous with adjacent cortical surfaces

X-ray appearance

Plain radiographs:

  • Interosseous border: Appears as a linear cortical thickening along the shaft

  • Contour: Sharp or slightly ridged margin facing the paired bone

  • Best visualized on: AP and lateral views of forearm or leg

  • Differentiation: Distinct from fractures due to smooth, continuous outline

CT appearance

Non-contrast CT:

  • Interosseous border: Well-defined cortical ridge along the diaphysis

  • Cortical thickness: Increased compared with adjacent surfaces

  • Orientation: Clearly directed toward the paired bone

  • Utility: Excellent for evaluating cortical integrity and subtle contour variations

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal intensity forming a sharp linear margin

  • Adjacent marrow: High signal intensity

  • Interosseous membrane attachment: Seen as a thin low-signal band

T2-weighted images:

  • Cortex: Low signal

  • Surrounding soft tissues: Intermediate-to-high signal

  • Membrane: Low-signal linear structure bridging paired bones

STIR:

  • Fat suppression: Uniform suppression of marrow fat

  • Interosseous border: Remains sharply defined as low signal

  • Interosseous membrane: Clearly delineated against suppressed marrow

Proton density fat-saturated (PD FS):

  • Bone marrow: Suppressed fat signal

  • Cortex: Low signal ridge

MRI image

Interosseous border mri anatomy labelled image-img-00000-00000