Fibrous sheaths of toes

The fibrous sheaths of the toes are specialized connective tissue structures that envelop the flexor tendons along the plantar aspect of each toe, providing both mechanical support and guidance for tendon movement. These sheaths are composed of strong, collagenous fibers that form a tunnel-like structure, anchoring to the phalanges and the plantar plates at the metatarsophalangeal joints. The sheaths are reinforced by sagittal septa, which are extensions of the deep fibers of the plantar aponeurosis, connecting to the deep transverse metatarsal ligament and the proximal phalanges. This arrangement stabilizes the flexor tendons and prevents bowstringing during toe flexion.

In the region proximal to the metatarsal heads, the fibrous sheaths are integrated with transverse bands (retinacula cutis) and sagittal septa, which help distribute mechanical forces and anchor the skin to the underlying skeleton. Distally, the sheaths are connected by the plantar interdigital ligament and a mooring ligament, which arch from one fibrous sheath to the next, further stabilizing the digital structures. Vertical fibers from joint capsules and the sides of the fibrous sheaths contribute to the formation of cushions beneath each metatarsal head, protecting neurovascular bundles as they traverse the forefoot.