How does an osteochondral lesion occur?
An osteochondral lesion, previously known as osteochondritis dissecans, occurs secondary to inversion or eversion injuries of the ankle, and is a direct result of the tibia contacting the talar dome. As the name implies, there is injury both to the bone and the overlying hyaline articular cartilage. MRI is useful not only to recognize these lesions, but also to characterize them as stable or unstable, using well-studied criteria.
The specific MRI findings that suggest that an osteochondral lesion is unstable are:
- • Linear high signal intensity surrounding the fragment on fluid sensitive images
- • Large cysts deep to the fragment
- • Absence of the fragment from the donor site