Yes, MRI is the best non-invasive imaging tool available for seeing cartilage. Unlike X-rays or CT scans, which primarily show bone, MRI excels at visualizing soft tissues, and cartilage is one of the structures it captures in considerable detail. A standard knee MRI, for example, can reveal the thickness, surface integrity, and internal structure of the cartilage lining your joints.
How Cartilage Appears on MRI
On MRI, healthy cartilage shows up as a smooth, well-defined layer coating the ends of your bones. Its exact brightness depends on the type of MRI sequence used. On proton density-weighted images, the most useful sequence for cartilage evaluation, cartilage appears as an intermediate-brightness band with good contrast against both the bright joint fluid and the darker bone beneath it. On another common sequence type called fat-suppressed gradient echo imaging, cartilage appears bright while the surrounding fluid, bone, fat, and muscle all look relatively dark.
With high-resolution techniques, radiologists can actually distinguish three separate layers within healthy cartilage: a dark surface layer, a brighter middle layer, and a dark deep layer that transitions into bone. This layered pattern is easiest to see in thicker cartilage areas like the kneecap and the groove it slides through on the thighbone.
What MRI Reveals About Cartilage Damage
When cartilage is damaged, MRI can pick up several telltale signs. Surface irregularities like fissures and cracks show up as disruptions in the normally smooth cartilage outline. Areas of cartilage softening, an early sign of breakdown, often appear as focal regions of decreased signal on fluid-sensitive sequences. Thinning of the cartilage layer compared to surrounding areas suggests degeneration, though there is natural variation in cartilage thickness between healthy individuals.
MRI also captures changes in the bone directly beneath the cartilage, which are important clues about cartilage health. Swelling-like signals in the bone marrow often accompany acute cartilage injuries, while cysts and bone spurs suggest longer-standing damage. Radiologists use a standardized grading scale from 0 to 4 to describe what they see:
- Grade 0: Normal cartilage with a smooth surface and uniform layered appearance.
- Grade 1: Early changes, either abnormal signal within the cartilage without visible shape changes, or minor surface fissures.
- Grade 2: A focal defect involving less than half the cartilage thickness.
- Grade 3: A defect extending through more than half the cartilage thickness but not reaching bone. This includes blistering, delamination (where cartilage separates from bone), and cartilage flaps.
- Grade 4: Full-thickness cartilage loss exposing the underlying bone, typically with bone marrow swelling or cyst formation underneath.
What MRI Can Miss
MRI is good at seeing cartilage, but it is not perfect. Very subtle surface fissures can fall below the spatial resolution of even a quality scan, meaning they might only be visible during arthroscopy (a surgical camera inserted into the joint). The accuracy of cartilage thickness measurements on standard MRI carries an average error of roughly 0.3 millimeters, which matters when the cartilage layer itself may only be a few millimeters thick in some areas.
The joint being imaged also affects how well cartilage shows up. In the hip, for instance, the cartilage is thinner and the joint geometry is more complex. One study comparing imaging techniques in hip joints found that cartilage was not measurable at about 50% of evaluated points on standard MR arthrography, compared to nearly all points being measurable with CT arthrography. So for certain joints, your doctor may order a different type of scan or add a contrast injection to improve visualization.
How Scanner Strength Affects Image Quality
MRI scanners come in different strengths, measured in Tesla (T), and the strength matters for cartilage imaging. The two most common clinical scanners are 1.5T and 3T. A meta-analysis comparing the two found that 3T scanners are meaningfully better at detecting cartilage lesions. The 3T scanners achieved a sensitivity of about 85% and a specificity of about 70%, compared to roughly 83% sensitivity and 66% specificity for 1.5T machines. One large study of 200 patients found that 3T imaging improved overall accuracy from 74.5% to 80.1% compared to 1.5T.
If your doctor is specifically looking for cartilage damage, a 3T scanner provides a clearer picture. That said, 1.5T scanners are more widely available and still detect the majority of significant cartilage problems.
Hyaline Cartilage vs. Fibrocartilage
Your joints contain two main types of cartilage, and MRI handles them differently. Hyaline (articular) cartilage is the smooth, glassy coating on bone surfaces. This is what most people mean when they ask about cartilage on MRI, and it is the type that shows the layered appearance described above.
Fibrocartilage, like the meniscus in your knee or the labrum in your shoulder and hip, is a tougher, more fibrous tissue. It normally appears very dark on MRI because of its dense collagen structure. Tears in fibrocartilage show up as bright lines or areas of increased signal within this normally dark tissue, making them relatively straightforward to identify. MRI is highly reliable for detecting meniscal tears, generally more so than for grading articular cartilage damage.
Advanced Techniques for Early Detection
Standard MRI sequences show cartilage structure, but specialized techniques called quantitative mapping can detect cartilage breakdown before any visible damage appears. T2 mapping measures changes in water content and collagen organization within the cartilage. Because the earliest stages of cartilage degeneration involve disruption of the collagen network and increased water absorption, T2 mapping can flag biochemical deterioration while the cartilage still looks structurally normal on a standard scan.
Another specialized technique uses a contrast agent injected intravenously, then scans the joint after a delay of about two hours. The contrast agent distributes through the cartilage in a pattern that reflects the concentration of key structural molecules called glycosaminoglycans. Areas where these molecules are depleted, an early sign of osteoarthritis, take up more contrast and can be identified on the resulting images. These advanced techniques are primarily used in research settings and specialized centers rather than routine clinical scans, but they represent what is possible when early cartilage changes need to be caught.