A Guide to the Bones of Your Foot
Graphic copyright Jeremy Leslie-Spinks
Last time we zoomed in on your toes – this week we look at the rest of your foot. In today’s post we’ll take a trip from the toes to the ankle, which is where you find the anterior tarsals, five bones of varying shapes and sizes, which make up the instep, also known as the posterior transverse arch.
Fig. 1: Posterior transverse arch: (Graphic copyright Jeremy Leslie-Spinks)
The base of each toe articulates with the head of its metatarsal bone. Figure 2 illustrates the points at which your toes join your metatarsal bones, and where these join the anterior tarsus.
Fig. 2: Ventral view of right foot. (Graphic copyright Jeremy Leslie-Spinks).
There are five metatarsals (numbered from I to V, starting from the inner edge of the foot and working outwards). They vary in length; the longest is number II, followed by III, IV and V – the shortest and strongest is number I. They are held in place and supported by intrinsic muscles, as well as by a matrix of capsules, ligaments, and tendons. (We’ll look at muscles and tendons later — today is about bones, so you can visualise the internal structure of your beautiful, eminently practical feet).
Your anterior tarsus starts at the inner edge of your foot with three cuneiform bones, numbered I, II, and III, which articulate with metatarsals I, II and III. “Cuneiform” means wedge-shaped (Latin “cuneus” = wedge), and in fact their lower surface does taper down to a wedge, like the stones of an archway.
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At the outer edge of the foot is the cuboid bone, joining metatarsals IV and V. Behind the three cuneiforms is the navicular (meaning ship-shaped) bone, which at its outer edge also joins the cuboid. If you could look down at these bones from above, they would look like Figure 3.
Fig. 3: Dorsal view of right foot. (Graphic copyright Jeremy Leslie-Spinks)
Further back, towards the heel, are the ankle bone or talus and the heel bone, calcaneus, (from the Latin word “calx” = heel). The characteristics of these two bones are what govern our ability to dance, or even to walk at all. The talus is where the foot joins the leg, and its complex architecture allows different movements — your talus can literally rock and roll. It can tip from side to side in relation to the heel bone, or forwards and back between the bones of your lower leg. The Latin name “talus” refers to an antique kind of oblong-shaped dice which had rounded ends, and numbers only on four sides. Quite how people played with it I don’t know, but the talus in your ankle has concave and convex surfaces on its different facets, like a saddle.
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The curves and rounded shapes of this bone are slightly snail-like…
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…almost mushroom-ish…
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… a bit like this…
Graphic copyright Jeremy Leslie-Spinks
The surfaces of your talus interact with contact points on your navicular bone in front, your calcaneus below, and your tibia and fibula above. Options for movement here include “rolling in” (pronation), “rolling out” (supination), “pigeon-toes” (inversion), “winging” (eversion), “pointing” and “flexing” (plantar flexion and dorsiflexion), and combinations of these. Figure 4 shows the right ankle seen from above on the diagonal.
Fig. 4: Right ankle, anterolateral view. (Graphic copyright Jeremy Leslie-Spinks)
One very important aspect of this for dancers is the built-in safety feature. The curved upper surface of the talus is the trochlea, (from Latin by way of Greek – “τροχαλία” = pulley), and it is this curve which rocks in and out of the space between the bones of the lower leg. It resembles a rounded, raised platform, and it fits into the space between the lower ends of the tibia and fibula. These are held tightly together all the way from your knee to your ankle by a tough matrix of fibres, and just where they join your foot, there is a square space. You can see this in Figures 5 and 6, below.
Fig. 5: Joint between talus, tibia and fibula (Graphic copyright Jeremy Leslie-Spinks)
Fig. 6: Talus held between tibia and fibula https://pixabay.com/photos/radiography-diagnosis-anatomy-3057768/
The raised top of the talus is wider at the front than at the back, and the whole structure tilts back and forth in this square space. When your foot is in plantar flexion (on demi-pointe, for example), your talus rocks forwards, so that its narrow rear end slides into the space between tibia and fibula, allowing quite a lot of side-to-side movement. In this position your ankle is unstable (no surprise to dancers, who deal with the problem hundreds of times a day). In Figure 5, above, you can see the fibula and the tibia with the foot in partial plantar flexion, with the talus extending forwards from the square space between the two bones of the lower leg.
When you come down into demi-plié, the situation changes. Your talus slides back into the square space, so the wide end of the raised platform now fits exactly into the space between tibia and fibula, so perfectly that any side-to-side instability becomes impossible. Your upper ankle is now held securely in place. Demi-plié is a really safe position to be in, precisely because of the snug embrace of this joint. Figure 7, below, shows the ankle dorsiflexed, as it would be in a deep demi-plié, and you can see that the talus is now right back inside the space firmly supported on both sides between tibia and fibula.
Fig. 7: Ankle in dorsiflexion, seen from right side (Graphic copyright Jeremy Leslie-Spinks)
When you look at your foot, you see it as a single object. Structurally, however, it is really divided lengthwise into two sections, and Figure 8 shows how this works. The red section of this foot shows the first three metatarsals articulating with the three cuneiform bones, and all of these are joined with the talus. In the blue section, metatarsals IV and V, have their base on the cuboid bone, which joins the calcaneus. From a skeletal point of view, they make up two quite distinct entities. This is one of the reasons why dancers instinctively align their weight over the first, second and third toe – everyone knows that uncomfortable moment when the weight falls on the outer edge of the foot, leaving you standing on your little toe, feeling weak and out of control. In fact, the metatarsals and toes spread out forwards from the ankle like the rays of the sun, and this is because the talus and the calcaneus are not lined up straight on top of each other – the calcaneus is angled slightly outwards, causing the metatarsals and toes to spread apart.
Fig. 8: Navicular-cuneiform and cuboid divisions of right foot (Graphic copyright Jeremy Leslie-Spinks)
These bony structures and their soft tissues make up the foot with which you can do such wonderful things. It’s a good foot, strong, resilient, reliable and incredibly versatile. With care and love, (and isn’t that what we all need?) it’ll be your faithful companion for all the amazing years of your dancing life…
©Jeremy Leslie-Spinks
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