Subchondral insufficiency fractures, subchondral insufficiency fractures with osteonecrosis, and other apparently spontaneous subchondral bone lesions of the knee —pathogenesis and diagnosis at imaging

AbstractSubchondral insufficiency fractures (SIFs) and SIFs with osteonecrosis (SIF-ONs) of the knee (previously misnamed spontaneous osteonecrosis of the knee (SONK)) are bone lesions that appear without prior traumatic, tumoral, or inflammatory event.Both conditions are characterized in the early stages by epiphyseal bone marrow edema (BME)-like signal at MRI. However, while SIFs usually heal spontaneously, they can also evolve to osteonecrosis (i.e., SIF-ON), which may progress to an irreversible collapse of the articular surface. Careful analysis of other MRI signs may help differentiate the two conditions in the early phase. In SIFs, the BME edema-like signal extends to the area immediately adjacent to the subchondral plate, while in SIF-ONs, this subchondral area shows low signal intensity on fluid-sensitive MR images due to altered bone marrow. The thickness and length of subchondral areas with low fluid-sensitive signal intensity are important factors that determine the prognosis of SIF-ONs. If they are thicker than 4  mm or longer than 14 mm, the prognosis is poor. The differential diagnosis of SIFs and SIF-ONs include bone lesions associated with the “complex regional pain syndrome” (CRPS), epiphyseal osteonecrosis of systemic origin, and those related to cartilage pathology.Clinical relevance statement  Imaging plays an essential role in diagnosing subchondral insufficiency fractures (SIFs) from subchondral insufficiency fractures with osteonecrosis (SIF-ONs...
Source: Insights into Imaging - Category: Radiology Source Type: research