MR imaging of the ankle and foot: normal structures and anatomic variants that may simulate disease

In the past, MR imaging of the ankle and foot has been performed by scanning both extremities simultaneously to provide a normal side for comparison. More recently, unilateral imaging with small local coils has been favored to maximize spatial resolution through use of small fields of view or large matrices. Such clarity of detail, however, demands a greater knowledge of normal anatomy and anatomic variants. We illustrate the MR appearances of a number of variants involving muscle, tendons, ligaments, and osseous structures of the foot and ankle. Familiarity with these findings is essential to prevent errors in the interpretation of MR images.