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Xiphisternal joint

The xiphisternal joint is the articulation between the body of the sternum and the xiphoid process. It is typically a synchondrosis (cartilaginous joint) in early life and later becomes a synostosis through natural ossification in adulthood. Located at the inferior end of the sternum, the joint marks an important surface anatomical landmark corresponding to the T9 vertebral level and the inferior border of the heart.

This joint contributes to the stability of the anterior thoracic cage, supports attachment of diaphragmatic fibers, and is involved in respiratory movement of the lower costal region.

Synonyms

  • Xiphisternal synchondrosis

  • Sternal xiphoid junction

  • Sternal–xiphoid joint

Location and Structure

  • Position: At the inferior end of the sternum where the body meets the xiphoid process.

  • Joint type:

    • Synchondrosis in youth (cartilaginous union)

    • Synostosis in adulthood (fusion)

  • Composition:

    • Hyaline cartilage between the sternal body and xiphoid early in life

    • Gradual ossification leads to bony union

  • Shape: Slightly angulated anteriorly, contributing to the infrasternal angle.

Relations

  • Anteriorly: Sternocostal fascia and subcutaneous tissue

  • Posteriorly: Diaphragm origins and anterior surface of pericardium (via central tendon attachments)

  • Superiorly: Body of sternum

  • Inferiorly: Xiphoid process

  • Laterally: Inferior costal cartilages and abdominal wall musculature

Attachments

  • Diaphragm: Sternal fibers originate near the xiphisternal junction

  • Rectus abdominis: Some fibers attach to the anterior xiphoid region

  • Linea alba: Midline tendinous structure anchoring to the xiphoid margin

  • Thoracic fascia: Covers anterior surface of joint

Function

  • Provides structural stability to the lower sternum

  • Serves as an anchoring point for diaphragm and abdominal musculature

  • Contributes to formation of the infrasternal angle

  • Assists in thoracic wall movement during respiration through its connection with diaphragm fibers

MRI Appearance

T1-weighted images:

  • Sternal body and xiphoid: Bright marrow signal due to fatty content in adults

  • Cortical margins: Dark low-signal lines

  • Cartilaginous or fused joint interface: Low to intermediate signal depending on degree of ossification

  • Soft tissues: Subcutaneous fat bright; diaphragm fibers intermediate

T2-weighted images:

  • Bone cortex: Dark low signal

  • Marrow: Intermediate-to-bright signal

  • Cartilaginous joint (younger individuals): Intermediate-to-bright signal

  • Fused joint (adults): Uniform low-signal bony bridge

  • Adjacent soft tissues: Diaphragm and fascia intermediate signal

STIR:

  • Bone and cortex: Low to intermediate

  • Marrow: Intermediate signal

  • Joint cartilage (if present): Intermediate-to-bright

  • Surrounding soft tissues: Fat suppressed, appearing dark

T1 Fat-Saturated Post-Contrast:

  • Normal bone: Mild uniform enhancement

  • Cartilage (when present): Minimal enhancement

  • Soft tissues: Enhancing fascia and muscular interfaces

  • Diaphragm: Mild enhancement of muscular fibers

  • No abnormal enhancement expected in normal joint

CT Appearance

Non-Contrast CT:

  • Cortical bone: High attenuation, sharply marginated

  • Marrow: Lower attenuation relative to cortex

  • Joint:

    • In younger individuals: visible low-attenuation cartilage between sternum and xiphoid

    • In adults: complete or partial bony fusion

  • Surrounding structures: Diaphragm origin and anterior pericardial surface visible

Post-Contrast CT:

  • Bone: No intrinsic enhancement

  • Soft tissues: Mild enhancement of fascia, diaphragm, and surrounding musculature

  • Joint region: Appears unchanged except for improved soft-tissue contrast

MRI image

Xiphisternal joint coronal MRI image-img-00000-00000

MRI image

Xiphisternal joint MRI sagittal image

CT image

Xiphisternal joint coronal ct image-img-00000-00000