A young adult patient presented with continued pain following an ankle injury despite conservative management. Radiograph of the left ankle (A) demonstrates a cortical defect with separation of an osseous fragment from the lateral talar dome (arrow). Coronal T1 (B) and proton density (PD) with fat suppression (C) images show the focal defect (arrows) with associated low T1 signal and high signal on PD between the articular cartilage and subchondral bone.
Osteochondral defect (OCD) of the talus occurs when an isolated fragment of articular cartilage and subchondral bone are detached, resulting in a loose body. Trauma remains the primary etiology secondary to acute traumatic event or repetitive loading injuries. Symptomatic OCD typically presents with chronic ankle pain, stiffness, and/or catching. Radiographic findings may initially be negative or underestimate the extent of injury. Thus, MRI is considered the modality of choice, particularly in determining instability and indications for orthopedic intervention. Stable fragments will show decreased signal intensity involving the junction of the fragment and subchondral bone on T2 sequences, which indicates healing. Unstable lesions have interposed high signal on T2 sequences, as in this case. Viability of the fragment can be assessed on T1 sequences. Necrosis is evident when the fragment has low T1 signal intensity on all sequences or does not enhance.1
At the Viewbox: Osteochondral Defect, Unstable. J Am Osteopath Coll Radiol.