Purpose: To determine if altered weight bearing causes the appearance of marrow edema on magnetic resonance (MR) images.
Materials and methods: Twelve volunteers underwent MR imaging with a short inversion time inversion-recovery (STIR) sequence at 1.5 T. The hips, knees, ankles, and feet were evaluated before and 2 weeks after altered weight bearing achieved with overpronation of one foot. Three volunteers underwent imaging a third time, 2 weeks after overpronation was stopped. Two observers assessed the images for evidence of marrow edema.
Results: Changes were seen on images in 11 volunteers; the overpronated side only was affected in 10. Most changes occurred in the foot followed by the tibia and the femur. Most changes were a diffuse increase in marrow edema. In two volunteers, the changes resembled those of stress fractures.
Conclusion: Altered weight bearing should be added to the list of causes of increased medullary signal intensity (ie, marrow edema) on MR images.