Cartilage Imaging in MRI – Appearance, Sequences, and Clinical Importance

Cartilage is a specialized connective tissue that plays a vital role in smooth joint movement and shock absorption. Among all imaging modalities, MRI is the best technique for evaluating cartilage, as it provides excellent soft tissue contrast and allows early detection of cartilage degeneration.

This article explains how cartilage appears on MRI, which sequences are used, advanced cartilage mapping techniques, and common imaging challenges.

1. How Cartilage Appears on MRI

On MRI, cartilage appears as a smooth, well-defined layer covering joint surfaces.

Signal Characteristics

T1-weighted images: Intermediate to low signal
T2-weighted images: Intermediate signal
PD-weighted images: Best contrast for cartilage thickness
Fluid-sensitive sequences (PD FS / T2 FS): Highlight cartilage defects

🔍 Normal cartilage is uniform in thickness with a smooth surface and sharp margins.

2. MRI Sequences for Cartilage Imaging

Different MRI sequences are used to assess cartilage morphology and pathology:

Commonly Used Sequences

Proton Density (PD)
PD Fat-Suppressed
T2-weighted
T2 Fat-Suppressed
Gradient Echo (GRE)
3D SPGR / DESS (for thin cartilage)

📌 PD Fat-Sat is most commonly used for joint cartilage evaluation.

3. Cartilage Mapping MRI – T1, T2, dGEMRIC

Cartilage mapping allows quantitative assessment of cartilage composition before visible damage occurs.

T2 Mapping

Evaluates collagen fiber integrity
Increased T2 values indicate early degeneration

T1 Mapping

Assesses proteoglycan content
Lower T1 values suggest cartilage damage

dGEMRIC (Delayed Gadolinium-Enhanced MRI of Cartilage)

Uses contrast agent
Measures glycosaminoglycan (GAG) content
Helpful in early osteoarthritis detection

🧠 Key Advantage: Detects biochemical changes before morphological defects appear.

4. Why Cartilage Is Not Visible on X-Ray

X-ray imaging depends on tissue density.

Reasons Cartilage Is Invisible

Cartilage is radiolucent
Lacks calcium and mineral content
Only bones are visible

📌 On X-ray, cartilage is assessed indirectly by joint space width.

5. CT vs MRI for Cartilage Evaluation

Feature	CT	MRI
Cartilage visibility	Poor	Excellent
Soft tissue contrast	Low	High
Early degeneration	Not detected	Detected
Radiation	Yes	No

👉 MRI is the modality of choice for cartilage evaluation.

6. Role of MRI in Early Cartilage Degeneration

MRI can detect early cartilage changes before symptoms worsen.

Early MRI Findings

Signal heterogeneity
Focal thinning
Surface irregularity
Increased T2 signal

🩺 Early detection helps in:

Preventing osteoarthritis
Monitoring athletes
Planning cartilage repair procedures

7. Common MRI Artifacts in Cartilage Imaging

Artifacts can mimic cartilage pathology.

Common Artifacts

Magic angle effect (false high signal)
Partial volume artifact
Motion artifacts
Susceptibility artifacts

📌 Proper positioning, thin slices, and optimal sequences help reduce artifacts.

8. Normal vs Abnormal Cartilage on MRI

Normal Cartilage

Smooth surface
Uniform thickness
Homogeneous signal
Well-defined margins

Abnormal Cartilage

Thinning or focal loss
Surface fissures
Signal heterogeneity
Subchondral bone changes

⚠️ Advanced cases show full-thickness cartilage loss with exposed bone.

Conclusion

MRI plays a crucial role in cartilage imaging, offering both morphological and biochemical evaluation. Advanced techniques like cartilage mapping MRI allow early detection of degeneration, helping clinicians intervene before irreversible joint damage occurs.

For radiology professionals, mastering cartilage MRI interpretation improves diagnostic accuracy and patient outcomes.

Tuesday, December 23, 2025