The flexor retinaculum (laciniate ligament) forms the fibro-osseous roof of the tarsal tunnel, converting the space behind the medial malleolus into a tunnel through which the posterior tibial tendon, FDL, posterior tibial artery and vein, tibial nerve, and FHL pass from the posterior leg to the foot. Its division in tarsal tunnel release decompresses the tibial nerve to treat tarsal tunnel syndrome.
| Origin | Medial malleolus |
|---|---|
| Insertion | Calcaneus (medial surface) |
| Actions | Forms the tarsal tunnel roof — constrains the tibialis posterior, FDL, tibial artery and nerve, and FHL tendons in their compartments as they pass behind the medial malleolus |
|---|
Tarsal tunnel syndrome involves tibial nerve compression under the flexor retinaculum from ganglion cysts, varicosities, accessory muscles, or post-traumatic fibrosis producing plantar burning, numbness, and intrinsic foot muscle weakness. The mnemonic Tom Dick AND Harry (Tibialis posterior, flexor Digitorum longus, posterior tibial Artery and vein, tibial Nerve, flexor Hallucis longus) remembers the tarsal tunnel contents from anterior to posterior.
Tibial nerve compression under the flexor retinaculum producing plantar foot burning and numbness managed with injection and surgical retinaculum division for refractory cases.
