The long plantar ligament is located within the base of the foot. It is the longest ligament  — connective tissue that usually joins bones — associated with bones in the foot. This ligament, combined with the plantar calcaneonavicular ligament and the plantar calcaneocuboid ligament, assists in forming the arch of the foot.

The long plantar ligament extends from the calcaneus (heel bone) to the cuboid bone, which is on the outside of the foot.

Plantar fasciitis is defined as inflammation of the plantar fascia, thick connective tissue that runs along the sole of the foot. However, this condition may actually result from damage to  the long plantar ligament, which exists in a similar location. This damage may result from physical activity, particularly that which pulls or stretches the ligament, such as kicking or jumping.

Patients with plantar fasciitis usually experience pain in the posterior arch of the foot, near the heel. Ice is traditionally used to reduce the inflammation, and the mid-foot may be taped up to support the arch. When the heel is affected instead of the arch, that area of the foot may be injected with steroid medication. Doctors advise that patients minimize bearing weight on the arch after an injury.