Spring ligament of the ankle: normal MR anatomy.

The plantar calcaneonavicular or spring ligament is visualized inconsistently and incompletely on routine MR images of the foot. This ligament is a vital stabilizer of the longitudinal arch of the foot, providing support for the head of the talus, which rests on the ligament's central portion. Laxity or rupture of the spring ligament permits plantar flexion of the talus. This motion results in valgus alignment of the calcaneus and a flatfoot deformity (pes planovalgus). Laxity or rupture of the spring ligament can develop in cases of chronic dysfunction of the posterior tibial tendon. In rupture of the posterior tibial tendon, surgical management may include plication of the spring ligament in addition to repair or reconstruction of the tendon to stabilize the medial column of the foot. Thus, the status of the spring ligament can be a significant consideration in preoperative planning. This pictorial essay illustrates the normal MR anatomy of the spring ligament, the planes of imaging required for optimal depiction of the ligament, and the neighboring structures with which the ligament can be confused.