Figure 1. (A–C) A 60-year-old woman presented due to left knee and calf pain, subsequently found to be caused by ECD. (A, B) MRI of the left knee showing innumerable T1-dark (A) and proton-density-bright (B) marrow-replacing lesions throughout the distal femur, proximal tibia, and proximal fibula (example lesion denoted by arrows). The patient also had small meniscal tears of the knee. (C) Follow-up MRI of the pelvis demonstrating additional lesions (arrowhead).