Ligamentum Plantare Longum
Descriptionligament is the longest and strongest ligament of the foot. Running along the base of the foot from the heel bone (calcaneus) to the base of the metatarsal bones, it assists in forming the longitudinal arch of the foot and keeping the calcaneocuboid joint and the midtarsal (Chopard) joint stable.   Deeper to the long plantar ligament lies the short plantar ligament. Follow this link to view a 3D model of the ligament.
Originating from the bottom surface of the calcaneus, adjacent to the Processus medialis tuberis calcanei, the long plantar ligament forms a flat, fibrous ligament that attaches at the base of the second to fifth metatarsal bones, and the posterior cuboid bone. 
The long plantar ligament closes the Sulcus tendinis musculi fibularis (peronei) longi, which is a meatus running along the base side of the cuboid bone and the three cuneiform bones. This meatus guides the tendon of the long peroneal muscle, which inserts at the base of the first metatarsal and is secured in this sulcus by the long plantar ligament.  Alongside the plantar calcaneonaviculare ligament and the plantar aponeurosis, the long plantar ligament passively supports the longitudinal arch of the foot. 
Additionally, the long plantar ligament serves as origin to some of the small foot muscles, and fortifies the capsula of the talotarsal joint.
Injuries to the long plantar ligament, especially if occurring in combination with injuries to other plantar ligament structures, can result in a destabilisation of the longitudinal arch of the foot.
Pain on the sole of the foot can indicate a tear or overload of the plantar ligaments or plantar fasciitis. These conditions are often caused by long periods of standing, overstressing of the foot due to overweight, foot malpositioning, or tense / short muscles of the calf.
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