Anatomy of the Cuboid Bone

The cuboid is a cube-shaped bone that is located on the outside portion of the foot, in front of the heel. The cuboid serves as an attachment point for muscle and functions as a pulley that helps point your foot downward. It also assists with mobility in the lateral (outer) column of the foot.

While fractures of the cuboid are uncommon, they can occur infrequently in specific circumstances. In addition, a rare, but painful condition called cuboid syndrome can occur when a subluxation (partial dislocation) occurs at the joint between the heel and cuboid.  

This article discusses the anatomy and function of the cuboid bone. It also covers associated conditions and when you may need treatment.

Anatomy

The human foot is an intricate structure that contains 26 bones, 33 individual joints. It also contains over 100 muscles (tissues that pull on joints so you can move), ligaments (bands of tissues that connect bone to bone), and tendons (bands that connect muscle to bone).

The cuboid bone is one of five that form the midfoot, the center area of your foot. The others are the navicular, lateral, medial, and intermediate cuneiform bones.

Structure

The cuboid bone gets its name from the fact that it's roughly the shape of a cube. It also contains a boney prominence, the tuberosity of the cuboid, that sticks out toward the sole of the foot.

Blood supply to this foot bone comes from the lateral plantar artery, a blood vessel that branches off the posterior tibial artery that delivers oxygenated blood to the lower leg and foot.

Several different ligaments help stabilize the cuboid. They include the:

• Calcaneocuboid ligament
• Cuboideonavicular ligament
• Cuboideo-metatarsal ligament
• Long plantar ligament

The bone also has one muscular insertion. The tibialis posterior muscle travels from the lower leg and attaches to the underside (plantar) surface of the cuboid.

The plantar and lateral surfaces of the bone also contain an important groove called the peroneal sulcus. This provides a boney roadway for the peroneus longus tendon to reach attachment points. These points are located at the first metatarsal and medial cuneiform, behind the bones in your big toe.

Location

The cuboid bone is situated on the outside border of the foot and connects with five other foot bones.

It forms a joint with the heel bone, or calcaneus, called the calcaneocuboid joint. Closer to the toes, it meets up with the fourth and fifth metatarsals.

As you move inward toward your foot's arch, the cuboid also connects to the navicular and lateral cuneiform bones.

Anatomical Variations

In rare cases, the cuboid and navicular bones can grow into one another. This is called a cuboid-navicular coalition. This usually starts before birth. If it causes any stiffness or pain, symptoms usually appear during late childhood or early adolescence.

It's usually treated conservatively with physical therapy or non-steroidal anti-inflammatory drugs (NSAIDs). For persistent or severe cases, surgery may be considered.

Function

The cuboid bone plays an important role in the foot’s stability and in your daily functioning. Its one muscular attachment, the tibialis posterior, helps to point the foot downward (plantar flexion).

This movement assists in propelling you forward as you take a step. The muscle also helps move the foot inward and supporting the foot’s arch structure.

In addition, the peroneus longus muscle, which passes through the peroneal sulcus in the cuboid, turns the foot outward. The muscle also assists with pointing the foot downward and plays a major role in your ability to balance.

Perhaps the most influential function of the cuboid is providing stability and support to the foot's outer edge. The bone is not directly involved with weight-bearing. However, standing and walking place a large amount of mechanical force on the cuboid, which it works to dissipate.

This allows the outside portion of the foot to be more mobile and adapt while walking on uneven surfaces.

Associated Conditions

Because it sits in a fairly protected area in the foot and is not directly involved with weight-bearing, the cuboid is not a frequently injured area. That said, there are several conditions that can affect the bone.

Cuboid Syndrome

One of the more common conditions for this bone is cuboid syndrome. This condition occurs when the calcaneocuboid joint is partially dislocated. It's usually caused by an ankle sprain or by excessive, repetitive rolling inward of the foot.

People affected by this syndrome usually experience:

• Pain on the outside edge of the foot (especially when walking)
• Bruising
• Swelling
• Limited range of motion of the foot

In the case of cuboid syndrome, imaging is not typically of value. Instead, your healthcare provider may diagnose it after an evaluation in the office.

Cuboid Fracture

Infrequently, the cuboid bone can also be fractured. While rare, this is typically the result of a heavy object falling on top of the foot and usually occurs alongside multiple other foot injuries.

This type of fracture, sometimes referred to as a nutcracker fracture, can also happen when the foot is excessively pointed and rolled outward.

Repetitive loads on the foot can also lead to a cuboid stress fracture. These forces can occur with sports like endurance running, gymnastics, or basketball. Chronic stresses on the lateral foot cause a mechanical failure of the bone.

Regardless of the type of fracture, the symptoms very closely mirror those seen in cuboid syndrome. The most common complaints are:

• Tenderness over the bone
• Swelling
• Redness or bruising
• Difficulty walking or participating in sports

For cuboid fractures, a magnetic resonance imaging (MRI) scan can be helpful in properly visualizing and diagnosing the injury. This is especially true in stress fractures, which can be challenging to see on X-rays.

Rehabilitation

Cuboid syndrome is typically managed conservatively with padding to the cuboid area and physical therapy. A healthcare provider may use a cuboid manipulation technique to help relocate the bone after a partial dislocation and reduce your pain.

A cuboid fracture is also typically treated conservatively. You'll keep weight off of it for a period of time followed by a transition into a walking boot. Ultimately, the boot is discontinued and physical therapy is initiated to regain foot range of motion, rebuild strength, and guide your return to running or jumping.

Fortunately, the cuboid bone has a rich supply of blood so this type of fracture is among the quickest in the foot to heal. Infrequently, fractures that don't heal or that affect the length or function of the foot's lateral column may need surgery.

Surgical techniques may include:

• Open reduction internal fixation: Hardware is inserted to hold the bone internally while it heals
• External fixation: Hardware is inserted in the bone and held with a frame outside of the skin
• Bone graft: Uses bone from another location to help fill space and maintain length
• Joint fusion: Joins together two bones from a joint

Be sure to speak to your healthcare provider if you experience a lateral foot injury so they can properly diagnose and treat your condition. 

Summary

The cuboid is a bone that's located on the outer edge of the foot in front of the heel. It helps to stabilize and provide support for the outer edge of the foot. The muscle that's attached to the cuboid helps you point your foot downward, which assists with walking.

Medical conditions that can affect the bone include cuboid syndrome and cuboid fractures. With both conditions, conservative treatment, including physical therapy, is usually recommended. In some cases, fractures may require surgery.