Midtarsal break
Also called: Flexible midfoot · Bendy feet · Midfoot break
A foot that bends in the middle, between the heel and the ball, as well as at the toes. About 1 in 12 people have it. It looks like the midfoot bend of apes.
How common
Can you do this?
How it works
In most people the middle of the foot stays stiff as the heel lifts. The foot then acts as a lever that pushes off from the ball and toes2. The stiffness pushes you forward with little wasted effort.
Chimpanzees and other apes have a different foot. Their midfoot bends upward as the heel lifts. The bend comes from several joints in the middle of the foot3. This bend is called a midtarsal break. A mobile midfoot helps apes climb trees2.
Some humans have it too. In 2013 Jeremy DeSilva and Simone Gill at Boston University filmed 398 adults walking barefoot across a pressure-sensing mat. Some of them showed a clear bend in the midfoot as they pushed off2. These people had flatter arches. Their weight also rolled more onto the inner edge of the foot, which is called pronation12.
It is not known to cause pain or injury. It looks like the bend in an ape foot. It is not known whether it is a leftover from tree-climbing ancestors.
How common it is
The 8% figure comes from one study in 2013. It filmed 398 adults walking barefoot across a pressure mat, and 32 of them had the trait2. The true rate in other populations, or in people wearing shoes, is not known. The researchers linked the trait to flatter arches and pronation, which suggests the rate could differ between groups with different foot shapes, but nobody has tested that directly2.
Try it
- Take off your shoes and socks. Stand on a hard floor.
- Ask someone to film your foot from the side, at floor level, while you walk slowly.
- Watch the middle of the foot as the heel lifts. In most people the foot stays straight from heel to ball until the heel is well off the ground.
- If the heel lifts while the middle of the foot stays on the floor, the foot bends in the middle. That bend may be a midtarsal break.
Is it a problem?
No. A midtarsal break is a normal variation in foot structure, not an injury2.
Mention it to a doctor if a foot bends in the middle along with:
- pain,
- swelling,
- a feeling of instability when you walk.
Those signs point to a joint or ligament problem, not this trait.
Sources and further material
- Wikipedia Arches of the foot The arches of the human foot. People with flat feet tend to walk with the foot rolled inward, which is called pronation.
- doi.org A midtarsal (midfoot) break in the human foot American Journal of Physical Anthropology 151(3):495-499. 32 of 398 people had a midtarsal break. They had flatter feet and more pronation.
- doi.org Revisiting the "midtarsal break" American Journal of Physical Anthropology. In apes, about two thirds of the midfoot bend is at the cuboid-metatarsal joint.
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Related oddities
Joint hypermobility
About 1 in 5 people have joints that bend further than usual, measured with a nine-point test called the Beighton score. For most people it causes no trouble.
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Two toes joined by skin, most often the second and third, in about 1 in 2,000 to 2,500 babies. The toes usually work normally and many people leave them as they are.
Morton's toe
A second toe that looks longer than the big toe because the first metatarsal bone in the foot is short. It is common, and it is the foot shape seen on classical Greek statues.
Knuckle cracking
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