Figure 1: Magnetic resonance imaging of lumbar spine, sagittal T2-weighted images (a-c), axial T2-weighted fat spin echo (FSE) image (d). (a) Sagittal magnetic resonance images showing a heterointense mass-like lesion (arrowheads) located in the L5/S1 facet joint. Lumbar facet joint hematoma was first considered due to sudden onset of symptoms and hemophilia history. There is no herniated intervertebral disc or dehydrated disc. (b and c) Hematoma was gradually resolved at 3 months (b) and 9 months (c) after conservative treatment. (d) The sagittal image shows complete resolution of hematoma at 4-year follow-up