https://youtube.com/shorts/8ApMUe7aktc
Why This Matters
In adult osteochondritis dissecans, instability is not defined by fragment displacement.
It is a biological problem, and MRI allows us to recognize instability before mechanical failure occurs.
Core Principle
In adults, even ONE MRI instability sign = Unstable OCD
Waiting for displacement means the biological window for healing is already gone.
Key MRI Findings of Unstable OCD
High-signal-intensity rim (T2)
• Fluid or granulation tissue at the fragment–host bone interface
• Strongest and most reliable predictor of instability
Subchondral cystic changes
• Juvenile OCD: size and number matter
• Adult OCD: presence alone is concerning
Cartilage breach
• High-signal line extending through the articular cartilage
• Indicates failure of the entire osteochondral unit
• Biological healing is extremely unlikely
Outer low-signal-intensity rim (T2)
• Fibrous tissue or sclerosis at the interface
• Reflects chronic biological separation, even if the fragment looks in place
โ๏ธ The Sleigh-Bell Sign
• Thin, lamellar osteochondral fragment
• Clear circumferential demarcation
• Appears to “hang” from the host bone
This is not a fragment that is loosening.
It is already biologically detached, even without displacement.
Pathologically, the fragment is dead in situ—
mechanically present, but without blood supply or healing potential.
Take-Home Message
Not displaced ≠ stable
When MRI shows instability in adult OCD,
the ending has already been written.
#DrSlothic #SlothicRadiology #UnstableOCD #OsteochondritisDissecans #KneeMRI #MSKRadiology #OrthopedicImaging #SportsRadiology #RadiologyEducation #MRITeaching
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