Cuboid bone

The cuboid bone is one of the seven tarsal bones of the foot, located on the lateral aspect of the midfoot. It is roughly cube-shaped, which gives it its name. The cuboid forms a key part of the lateral longitudinal arch and serves as a stabilizing structure that links the hindfoot and forefoot. It articulates with the calcaneus posteriorly, the lateral cuneiform and navicular medially, and the bases of the fourth and fifth metatarsals anteriorly. It is also traversed by the tendon of the fibularis longus muscle, making it essential for foot stabilization and eversion.

Structure

The cuboid is an irregular six-sided bone with articular and non-articular surfaces. Its dorsal surface is relatively flat and accessible, while the plantar surface contains a deep groove for the fibularis longus tendon. The bone is surrounded by ligaments and has cortical bone externally and cancellous bone internally. It is relatively compact and durable to handle the tensile forces during gait and weight-bearing.

Surfaces and Features

• Dorsal surface: Flat and subcutaneous, contributes to the dorsal contour of the midfoot.
• Plantar surface: Features the fibular (peroneal) groove, which houses the fibularis longus tendon. A prominent ridge lateral to the groove provides leverage and protection to the tendon.
• Posterior surface: Articulates with the anterior surface of the calcaneus to form the calcaneocuboid joint.
• Anterior surface: Articulates with the bases of the fourth and fifth metatarsals.
• Medial surface: Articulates with the lateral cuneiform and occasionally with the navicular.
• Lateral surface: Non-articular and continuous with the lateral aspect of the foot; serves as the origin for ligaments and fascia.

Location

The cuboid bone is located on the lateral side of the foot in the midfoot region. It lies anterior to the calcaneus, lateral to the lateral cuneiform, and posterior to the fourth and fifth metatarsal bases. Its plantar surface contributes to the floor of the lateral longitudinal arch and forms the lateral margin of the midfoot.

• Posterior: Calcaneus
• Anterior: Fourth and fifth metatarsals
• Medial: Lateral cuneiform, occasionally navicular
• Lateral: Fibularis longus tendon groove

Function

• Lateral arch support: Provides structural reinforcement to the lateral longitudinal arch of the foot
• Weight transmission: Helps transfer body weight from the calcaneus to the lateral metatarsals
• Stabilization of foot motion: Assists in midfoot stability, especially during propulsion and stance phase
• Tendon guidance: The fibularis longus groove acts as a pulley, enhancing foot eversion and arch support

Articulations

The cuboid articulates with five bones:

Bone	Joint	Type
Calcaneus	Calcaneocuboid joint	Synovial saddle (modified plane)
Lateral cuneiform	Cuboid–cuneiform joint	Synovial plane
Navicular (occasionally)	Cuboid–navicular joint	Synovial plane (if present)
4th metatarsal	Tarsometatarsal joint	Synovial plane
5th metatarsal	Tarsometatarsal joint	Synovial plane

Ligament Attachments

The cuboid is stabilized by multiple strong ligaments that form part of the midtarsal and tarsometatarsal joints.

Ligament	Attachment	Function
Long plantar ligament	From calcaneus to cuboid and bases of metatarsals	Supports lateral longitudinal arch and fibularis longus tendon
Short plantar (calcaneocuboid) ligament	Calcaneus to cuboid	Stabilizes calcaneocuboid joint
Dorsal calcaneocuboid ligament	Calcaneus to dorsal cuboid	Reinforces lateral midfoot dorsally
Dorsal and plantar tarsometatarsal ligaments	From cuboid to bases of 4th and 5th metatarsals	Stabilize lateral tarsometatarsal joints

Muscle Attachments

The cuboid bone serves as a functional pulley but does not directly serve as a primary muscular insertion site. However, muscles associated with it include:

• Fibularis longus: Passes through the peroneal groove on the plantar cuboid, inserting on the medial cuneiform and base of 1st metatarsal. It uses the cuboid as a mechanical pulley.
• Flexor hallucis brevis: Originates partly from the plantar cuboid surface, contributing to big toe flexion.

Blood Supply

The cuboid receives blood primarily from branches of the:

• Lateral plantar artery: Supplies plantar and lateral aspects
• Dorsalis pedis artery: Provides dorsal branches to the superior surface
• Peroneal (fibular) artery: May give off perforating branches contributing to the cuboid’s blood supply

Nerve Supply

Innervation is from branches of the:

• Lateral plantar nerve: Supplies plantar surface and nearby ligaments
• Sural nerve: Provides cutaneous innervation to the lateral dorsal aspect of the foot
• Deep fibular nerve: Supplies dorsal articular branches

Ossification

The cuboid ossifies from a single center that appears early relative to other tarsal bones, often around birth or shortly afterward.

• Primary ossification center: Appears around 9–10 months gestation
• Fully ossified: Usually by 1 year of age

Clinical Significance

• Cuboid syndrome: A subluxation or irritation of the cuboid bone, often due to repetitive strain or lateral ankle sprains. Presents with lateral foot pain and tenderness near the peroneal groove.
• Fractures: May occur from direct trauma or axial load. Often part of midfoot crush injuries and may involve the calcaneocuboid or tarsometatarsal joints.
• Accessory cuboid ossicles: Occasionally present near the tuberosity, may be mistaken for avulsion fractures.
• Tarsometatarsal arthritis: Degenerative changes may affect the joints between cuboid and lateral metatarsals, causing lateral midfoot pain and reduced mobility.
• Flatfoot deformity: Dysfunction of fibularis longus or ligamentous laxity can lead to arch collapse, in which the cuboid plays a biomechanical role.

Imaging

• X-ray: Standard AP, lateral, and oblique views assess alignment, fracture, joint spacing
• CT scan: Offers detailed assessment of fractures, joint congruity, and cuboid malalignment
• MRI: Useful in detecting stress reactions, bone marrow edema, and surrounding ligament or tendon pathology
• Ultrasound: May help visualize peroneal tendons and dynamic abnormalities related to cuboid syndrome