The deep transverse metatarsal ligament is a thick fibrous band linking the plantar plates of the second through fifth metatarsophalangeal joints transversely between adjacent metatarsal heads. It runs in the plane of the plantar plates and, together with the interosseous muscles, maintains the integrity of the forefoot transverse arch.
Binds adjacent plantar plates and metatarsal heads together, resisting forefoot splay and maintaining the transverse spacing of the lesser metatarsals during push-off. The digital neurovascular bundles pass plantar to this ligament in each web space.
The digital nerves and vessels travel in the web spaces plantar to the deep transverse metatarsal ligament and dorsal to the superficial transverse ligament. Chronic compression of the interdigital nerve beneath the deep ligament, combined with repetitive traction, contributes to Morton neuroma formation. The ligament must be divided during neuroma excision to decompress the nerve. Attenuation of the ligament, particularly at the second web space, contributes to forefoot splay and MTP instability.
Entrapment and perineural fibrosis of the interdigital nerve, most common in the third web space, causing burning forefoot pain radiating to adjacent toes, reproduced by lateral metatarsal compression and web space palpation.
Attenuation of the ligament allows lateral splaying of the metatarsal heads, widening the forefoot and producing metatarsal pain, skin callus under prominent heads, and progressive lesser toe deformity.
