Medial Cuneiform
Short bone; appendicular skeleton
Also known as: First Cuneiform, Wedge Bone
Classification
Short bone; appendicular skeleton
Dimensions
The largest of the three cuneiform bones, it is wedge-shaped with the thin edge pointing upward and the thick base facing the sole of the foot.
Key Features
It looks like a chunky, irregular wedge. Its front face is large and kidney-shaped where it meets the first long toe bone. The inner side is rounded and can often be felt as a bump on the inside of the foot, while the outer side has small flat spots where it touches neighboring bones.
Similar Bones
It is often confused with the Intermediate or Lateral Cuneiforms. You can tell the Medial Cuneiform apart because it is significantly larger and has a distinctive L-shaped or kidney-shaped surface on one end, whereas the others are more strictly triangular.
Across Species
In many primates, this bone is shaped like a saddle to allow the big toe to be opposable, much like a human thumb. In humans, its flatter surface helps lock the big toe into a forward-facing position, which provides a stable platform for walking upright. In hooved animals like horses, these specialized foot bones are often highly reduced or fused to support a single toe.
Evolutionary History
This bone originates from the ancient tarsal bones of early land-dwelling vertebrates. As our ancestors transitioned from climbing trees to walking on the ground, this specific bone adapted from a flexible joint-supporting structure into a rigid, load-bearing pillar that maintains the inner arch of the foot.
Photography Tips
To identify this bone, take a photo from the side showing the inner arch of the foot. A top-down view is also helpful to see how it fits between the ankle bones and the long bones of the toes. Use a ruler or a coin for scale.