Anatomy For Runners: The Foot and Ankle

Welcome to my Anatomy For Runners series! With this I’m hoping to educate runners on their bodies so that they feel more empowered in staying healthy. Don’t worry, we’ll keep it light, fun, and focused on what you really need to know with a bias toward the runner’s body.

In this third installment of the series, we are talking all about the foot and ankle. If you have read any of my blogs in the past, you already know that I LOVE the foot and ankle. In fact, I’ve probably already written this blog piecemeal in other posts, but let’s bring it all together in one, nifty package (with a bow, of course).

The foot is made up of 26 bones, 30 joints, and over 100 muscles. Don’t worry, we won’t go over all of them, but this is an important fact to note, because the foot is structured this way to both be flexible and rigid. All of the bones and joints allow for adaptability over different types of surfaces and terrain. Sort of like the SUV of the body: it can get you to the grocery store and soccer practice as well as off roading, through the rain, snow, and ice. Weird analogies aside, our feet are designed to take us where we need to go.

We will divide the foot into 3 sections: the forefoot, midfoot, and rearfoot, for simplification purposes. The forefoot is where the long bones of the metatarsals are, and of course we have 5 of these, one for each toe. Of particular interest is the big toe joint, anatomically called the first metatarsalphalangeal joint, because of its important role in running and walking. More on that later. The midfoot is where the magic happens, and is comprised of several bones and joints. Here we have the navicular, three cuneiforms, and cuboid. Movement in the midfoot is what allows for adjustment to the ground, whether we need flexibility over uneven ground or rigidity to generate power to push us forward. The rearfoot works with the midfoot to produce the foot/ankle motions that we need, and includes the calcaneus and talus (the heel bone and another bone that sits on top of it).

To round out our bony anatomy, we have the ankle joint, which is where the tibia and fibula sit atop the talus. This is where ankle dorsiflexion (flexing the foot) and ankle plantarflexion (pointing the foot) occurs.

Moving on to the muscles, we’ll start with those that have origins up in the lower leg and tendons that cross into the foot. There are many degrees of movement, as we’ve previously discussed, and this all depends on the muscles working together. Starting on the front of the leg: the tibialis anterior muscle runs along the tibia, and has a tendon that crosses the ankle joint, attaching on the navicular. This pulls our foot up and allows clearance of the ground. Oftentimes this is the “shin splint” muscle. Here we also have the extensor hallucis longus, which is a fancy word for “muscle that pulls up the big toe” and the extensor digitorum longus, another fancy word for “muscle that pulls up the rest of the toes”. Predictably, the tendons of these muscles travel to their respective toes that they are responsible for. The peroneal muscle group is on the outer side of the lower leg, spanning most of the length of the fibula. There is a long tendon that travels behind the outer ankle bone and attaches on the fifth metatarsal. The peroneal muscle moves the foot/ankle toward the outside and plays an important role in stability along with other muscles. The tibialis posterior is on the opposite and inner side of the ankle (also a tendon that occasionally gets the name of shin splints when it’s painful), passing deeply along the tibia, around the inner ankle bone, and attaching on the navicular and medial cuneiform. This muscle actively moves the ankle inward, but importantly for us runners, it plays a big role in pronation control. I sometimes liken it to a “natural orthotic”, supporting the arch. Passing closely to the tibialis posterior are the flexor hallucis longus and flexor digitorum longus. Similarly to the other side of the ankle, those muscles control the big toe and other toes in the opposite direction of flexion.

There are so many muscles that are exclusively in the foot, but we will focus on the important ones. The quadratus plantae underlies the plantar fascia and helps to support the arch. Dysfunction in this muscle can often mimic plantar fasciitis. The remainder of the muscles provide more fine control of the big toe, little toe (pinky toe), and the toes in between. All of this to say that there are many other structures in the foot that can cause foot pain besides the plantar fascia.

The plantar fascia is a thick band of connective tissue that spans the heel to the midfoot. The tension in this tissue is influenced by the entire posterior chain of the body, as the fascial chain is relatively continuous from the heel all the way up to the base of the head. There is also a nerve passing through here called the medial plantar nerve.

Are you sold? Do you love the foot as much as I do? Hope you have a better understanding of the foot and ankle, and have an appreciation for how complicated it is! (why are the best things so complicated?)

Keep going, you got this!

Kacy Seynders, PT, DPT