Corpus: Flexor retinaculum of foot

The flexor retinaculum of the foot is a ligamentous structure composed of tight parallel-fiber connective tissue that stretches between the medial malleolus and the medial surface of the calcaneus (calcaneal tuberosity).

The flexor retinaculum of the foot is part of the deep layer of the fascia cruris, located cranially, and borders caudally on the plantar fascia. It also serves as one of the three origins of the abductor hallucis muscle.

2.1. Malleolar canal

The anatomical gap that forms between the retinaculum and the calcaneus is known as the malleolar canal. The tendons of the three deep flexor muscles of the foot and their tendon sheaths pass through this canal:

• Flexor digitorum longus muscle
• Tibialis posterior muscle
• Flexor hallucis longus muscle

The tendons transition from a vertical to an almost horizontal orientation immediately behind the medial malleolus. Additionally, the posterior tibial artery and vein, along with the tibial nerve, run through one of the compartments. Compression of the tibial nerve in this area can cause tunnel pain, known as tarsal tunnel syndrome.

The flexor retinaculum of the foot – with its compartments – serves to flexibly secure the tendons of the deep flexors of the foot, ensuring they maintain their position during movement without impairing function. This prevents the tendons from lifting and ensures optimal mobility.