How many bones in the human foot?

How many bones in the human foot?

You’re at the local pub, the room is buzzing with energy as the MC turns down Paul Kelly, and politely asks you to take your seat, Trivia is about the get under way!

As scribe you scurry to find a pencil, nestle in on your stool and greet your teammates. “let’s have a good one, if you know the answer, speak up”.

The MC clears his throat. “Question 1. How many bones are in the human foot?”

Ooo tricky. This is where X-ray vision would come in handy. Or you definitely could have counted them when you were last at the podiatrist staring at the colourful artwork of the human foot.

You with your supreme intellect know the answer is a bit of a hazy one. You know the MC has spent far more time in pubs than a library, and probably sourced his answer from google. Knowing this, here’s what I want you to answer.

26* however, there are the sesamoids and skeletal variations called Accessory Bones

Here’s why.

There are 26 regular bones of the foot. I could name them, but they’ve all got long Latin names, so you’ll just have to trust me.

The Sesamoids

The sesamoids are the forgotten bones of the foot but their role is quite important. We have two of them on each foot and they lie underneath the big toe joint. One is called the tibial sesamoid, the other the fibula sesamoid. They are the long-lost cousin of the knee cap and act in a similar fashion. They enhance the pull of the flexor halluces longus tendon which they are embedded within, helping to create a stronger big toe joint.
In some people, the sesamoids don’t fully develop and they are left with what is called a bipartite sesamoid. These sesamoids can be prone irritation and inflammation, particularly in people with a high arch foot type and playing jumping, landing and high intensity sports. These bipartitie sesamoids can sometimes be confused with a sesamoid fracture, however X-ray can help to determine how straight the adjacent edges are and if it is fractured or normal corticated bone.

We all have sesamoids, and for this reason, a good trivia master would answer 28.

Accessory Bones

Accessory bones or ‘ossicles’ as they are often referred, are normal variants of bone development that don’t often cause much pain or hassle. If you do have accessory bones in your feet, don’t be too alarmed, you’re not mutating into some futuristic beast. Recent studies describe 9-12 different locations for accessory bones, however there are up to 24 reported.

When they do cause pain, it is often in association with fracture, osteoarthritis, dislocations, degenerative changes, bone disease or impingement of the soft tissue nearby. They typically occur as a result of a failure of normal bone development such as non-union of a bone growth area.

One of the more common accessory bones of the foot is the Os Peroneum. It is a round or oval shaped sesamoid bone that is embedded in the peroneus longus tendon (tendon on the outside of the ankle) and sits next to the cuboid bone. “Os peroneum syndrome” can cause lateral foot pain, tenderness, and swelling along the peroneus longus tendon as well as lateral foot pain when pointing your foot down or sweeping it to the outside.

Another common accessory bone of the foot is the Os Naviculare. This additional bone sits next to or behind the navicular bone, in the arch of the foot. This can be troublesome because one of the main muscles of our inner ankle (Tibialis Posterior) attaches onto the navicular.

It is common to see people with a flat foot posture get pain at this site due to irritation of the tendon attachment onto the accessory navicular. We often get developing and active children that start to develop pain in this area.

Finally, the most common accessory bone of the ankle is the Os Trigonum. This bone sits deep in the ankle, behind the talus, and is a common cause of chronic ankle pain. This is often due to irritation of the connection of the talus and the os trigonum, or friction of the flexor halluces longus tendon as it wraps behind the ankle.

Other accessory bones include the Os Intermetatarseum (between the metatarsals), Os vesalianum pedis (next to the base of the 5th metatarsal), Os subfibulare (under the fibula), Os subtibiale (under the tibia), Os calcanei secundarium (on top of the heel bone), Os supratalare (on top of the talus), Os sustentaculi (behind the talus), Os talotibiale (inner front of the ankle joint), Os subcalcis (under the heel bone), Os supranaviculare (on top of the navicular).

As you can tell, they’ve all got pretty funky names that start with Os. However, we are thankful they provide a clue to their location in the foot or ankle, and not named after some old scientist or doctor (thanks Lis Franc).

So, next time you’re a bit stuck at trivia, show your supreme intellect and throw an asterisk on the end

26* however, there are the sesamoids and skeletal variations called Accessory Bones

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