Cuneiform Bones
Ossa Cuneiformia
location_on Medial midfoot, between the navicular and the first three metatarsals
The three cuneiform bones (medial, intermediate, and lateral) are wedge-shaped bones that form the middle of the foot's transverse arch. They are named for their triangular cross-section. The medial (first) cuneiform is the largest and articulates with the first metatarsal; the intermediate (second) is the smallest and is recessed, creating the keystone of the Lisfranc joint complex; and the lateral (third) cuneiform bridges to the cuboid.
Key Anatomical Features
- Three wedge-shaped bones: medial (largest), intermediate (smallest, recessed), and lateral
- Medial cuneiform is the largest and supports the first ray (great toe line)
- Intermediate cuneiform is recessed proximally, creating a mortise for the second metatarsal base
- Lateral cuneiform articulates with the cuboid laterally
- Together they form the transverse arch of the foot
- The Lisfranc ligament connects the medial cuneiform to the second metatarsal base
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| Tibialis anterior | Medial and inferior surfaces of medial cuneiform | Dorsiflexes and inverts the foot |
| Peroneus longus | Lateral surface of medial cuneiform (insertion site) | Everts the foot and plantarflexes the ankle |
| Tibialis posterior (slip) | Sends slips to all three cuneiforms | Plantarflexes and inverts the foot |
| Flexor hallucis brevis | Plantar surface of lateral cuneiform (partial origin) | Flexes the proximal phalanx of the great toe |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Naviculocuneiform joints | Synovial plane | Navicular |
| Tarsometatarsal (Lisfranc) joints | Synovial plane | First three metatarsals |
| Intercuneiform joints | Synovial plane | Adjacent cuneiform bones |
Common Pathologies
Lisfranc injury
Injury to the tarsometatarsal joint complex, ranging from ligament sprains to fracture-dislocations. The Lisfranc ligament connects the medial cuneiform to the second metatarsal base; its disruption causes instability.
Cuneiform fracture
Uncommon in isolation, usually associated with Lisfranc injuries or midfoot crush injuries. The intermediate cuneiform is most susceptible due to its recessed position.
First tarsometatarsal arthritis
Degenerative changes at the medial cuneiform-first metatarsal joint causing medial midfoot pain, especially in hallux valgus.
Midfoot osteoarthritis
Degenerative changes at the naviculocuneiform and tarsometatarsal joints, a common cause of dorsal midfoot pain and bony prominence.
Clinical Relevance
Lisfranc injuries are frequently missed in the emergency department (up to 20% misdiagnosis rate). A gap greater than 2mm between the first and second metatarsal bases on an AP weight-bearing foot radiograph suggests Lisfranc ligament disruption. Subtle injuries may only be detected on weight-bearing radiographs or CT/MRI. The recessed position of the intermediate cuneiform creates a keystone mortise effect that normally locks the second metatarsal base in place.
Development and Ossification
The medial cuneiform ossifies from a single center appearing around ages 2-3. The lateral cuneiform center appears around age 1, and the intermediate cuneiform center appears last, around ages 3-4. All three are cartilaginous at birth.
Did You Know?
- Cuneiform means wedge-shaped in Latin (cuneus = wedge), the same root as cuneiform writing from ancient Mesopotamia
- The intermediate cuneiform is the smallest of the three, yet its recessed position creates the critical mortise that stabilizes the midfoot
- Napoleon's surgeon Lisfranc described the tarsometatarsal joint as the best site for midfoot amputation in battle injuries, giving it its name
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