A 24-year-old basketball player lands awkwardly and sustains an OCD (osteochondritis dissecans) lesion of the medial femoral condyle. Which feature on MRI would indicate an UNSTABLE lesion requiring surgery?
- A T2 hyperintense signal line beneath the fragment ✓
- B Intact articular cartilage on T1 sequence
- C Lesion diameter <1 cm
- D Lesion located in the classic posterolateral aspect of medial femoral condyle
Correct answer: A. T2 hyperintense signal line beneath the fragment
Explanation
On MRI, a T2 hyperintense signal line beneath the OCD fragment (between fragment and parent bone) indicates fluid tracking behind the lesion, signifying instability — the fragment is separating. This is the most reliable MRI marker of instability and predicts that conservative management will fail. Intact articular cartilage (option B) suggests stability. Lesion size <1 cm generally favors healing with conservative management. Classic posterolateral location on the medial femoral condyle is the typical site but does not determine stability.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.