Intersesamoid ligament

At a glance

English

Intersesamoid ligament

Latin (TA2)

Ligamentum intersesamoideum

System

Ligament

Region

Foot

Side

Paired, left and right

About the intersesamoid ligament

The intersesamoid ligament is a small but dense band in the sole at the ball of the great toe. Under the head of the first metatarsal lie two pea-sized sesamoid bones, one medial and one lateral, and this ligament runs across the gap between them, linking their facing margins. It forms part of the thick fibrocartilaginous plate on the underside of the first metatarsophalangeal joint, so the two sesamoids and the band between them move as one unit with the base of the proximal phalanx.

Each sesamoid sits within the tendon of flexor hallucis brevis, the medial one in the tendon of its medial head and the lateral one in the tendon of its lateral head. The medial sesamoid also receives fibres of abductor hallucis, and the lateral one those of adductor hallucis. On the plantar face of the intersesamoid ligament, in the groove between the two bones, runs the tendon of flexor hallucis longus on its way to the distal phalanx. The ligament therefore forms the floor of a short channel that keeps this tendon centred under the joint.

The upper surfaces of both sesamoids carry cartilage and glide in grooves on the underside of the metatarsal head. By holding the pair at a fixed distance, the ligament keeps each bone tracking in its own groove as the toe bends and straightens. The sesamoids raise the flexor tendons away from the axis of the joint, improve their leverage, and take much of the load passing through the ball of the foot during push-off.

Rupture of this ligament, often as part of a wider tear of the plantar plate after forced dorsiflexion of the great toe, allows the sesamoids to spread apart. This is a feature of severe turf toe. Lateral drift of the sesamoids in hallux valgus also stretches the band.

Attachments and function

Attaches from

The lateral margin of the medial (tibial) sesamoid bone of the great toe.

Attaches to

The medial margin of the lateral (fibular) sesamoid bone of the great toe.

Function

Binds the two sesamoids together, keeps them tracking under the first metatarsal head, and floors the channel for the tendon of flexor hallucis longus.

Nerve supply

Articular branches of the medial plantar nerve to the first metatarsophalangeal joint.

Blood supply

Branches of the medial plantar artery and the first plantar metatarsal artery.