The long plantar ligament is the longest ligament in the foot, supporting the lateral column and forming the tunnel through which the peroneus longus tendon crosses the plantar midfoot to reach the medial cuneiform. Its deep portion reinforces the calcaneocuboid joint (the primary lateral column joint) and its superficial portion creates the peroneus longus tunnel. Attenuation of the long plantar ligament contributes to lateral column instability in progressive flatfoot.
| Origin | Plantar calcaneus (just anterior to the calcaneal tuberosity) |
|---|---|
| Insertion | Deep fibres: plantar cuboid. Superficial fibres: bases of the 2nd-5th metatarsals via the fibular (peroneal) tunnel |
| Actions | Primary stabiliser of the lateral longitudinal arch; restrains calcaneal abduction; superficial fibres form a tunnel for the peroneus longus tendon as it crosses the plantar foot |
|---|
The long plantar ligament is assessed in complete flatfoot evaluation — its attenuation on MRI (signal increase and thickening) indicates lateral column involvement beyond the typical medial PTTD and spring ligament failure. It can be incorporated in flatfoot reconstruction by direct repair or synthetic augmentation.
Long plantar ligament attenuation contributing to lateral arch collapse in severe flatfoot managed with lateral column reconstruction.
