By Elizabeth A. Murray, Mount St. Joseph University
Let’s take a look at the musculoskeletal anatomy of our feet. Regarding the insertions of muscles in the leg, we know that the origin is always proximal and the insertion always distal. Of the many muscles in the leg, all but popliteus cross the ankle joint and attach somewhere in the foot. In each foot there are seven tarsals, five metatarsals, and fourteen phalanges. And the tarsals, in particular, are linked together like pieces in a jigsaw puzzle.
Deltoid Ligament
Medially, at the hinge joint of the ankle, is a set of ligaments collectively referred to as the deltoid ligament. This is because they fan out like a triangle—like the Greek letter delta—from the medial malleolus of the tibia and attach to various tarsals.
This deltoid ligament can be broken down into four bands, and they provide good examples of ligaments with names that make sense: Notice that in each of these, tibio- is the ‘first name’ of the ligament, and the tarsal it connects to is its ‘last name’. There’s an anterior tibiotalar ligament, a posterior tibiotalar ligament, a tibionavicular ligament, and a tibiocalcaneal ligament. The anterior tibiotalar is deep to the tibionavicular, so can be difficult to see in images, depending on the view. This deltoid group is very strong and resists over-eversion of the foot.
This article comes directly from content in the video series How We Move: The Gross Anatomy of Motion. Watch it now, on Wondrium.
Lateral Collateral Ligament
On the lateral aspect of the ankle joint, there’s a series of three bands, with really no collective name, though they’re sometimes jointly referred to as the lateral collateral ligament. There’s an anterior talofibular ligament, a posterior talofibular ligament, and between them is a calcaneofibular ligament.
Notice that in a pattern similar to the naming of the bands of the deltoid ligament, these lateral ligaments all have the tarsal to which they attach as their ‘first name’, but have the fibula as their ‘last name’.
These lateral ligaments resist over-inversion of the foot, and are not nearly as strong as the ligaments of the medial ankle. The ankle joint has a thin anterior and posterior capsule, so its main reinforcements are on the sides, which is typical of a hinge joint.
Types of Joints
Within the foot itself, there are intertarsal joints, which are gliding joints between the various tarsals, as well as tarsometatarsal joints that link the distal row of tarsals to the five metatarsals; these are also gliding joints that allow planes of movement, like during inversion and eversion of the foot.
Moving distally, there are metatarsophalangeal joints—sometimes called MTP joints—between the heads of the five metatarsals and their proximal phalanges. These are condyloid joints in which the heads of the metatarsals are rounded and abut concave surfaces on the proximal phalanges.
Condyloid or ellipsoidal joints allow more movement than simple hinge joints. As a result, at the metatarsophalangeal joints, we get not only flexion and extension, but abduction, adduction, and even a bit of circumduction.
Within each toe are interphalangeal joints, called IPJs, with collateral ligaments on either side. There’s one interphalangeal joint in the big toe between its proximal and distal phalanx, and two interphalangeal joints in each of the smaller toes, which contain three phalanges each.
Talus and Calcaneus
The talus is said to have a head, neck, and cube-shaped body. While the body articulates with the tibia and fibula, the head faces anteriorly—or better said, distally. Some references indicate it as forming more or less a ball-and-socket joint with the concave surface of the boat-shaped navicular bone. Besides its role in ankle movements, the talus functions to transmit the standing weight of the body from the tibia to the other bones in the foot.
The calcaneus is the largest foot bone and forms the heel. Medially on the calcaneus is a small shelf called the sustentaculum tali, because it widens the calcaneus just inferior to its articulation with the talus.
Stress Fractures
The calcaneal tuberosity is a prominent attachment site on the inferior and posterior surface of the calcaneus. But the Achilles, or calcaneal, tendon attaches to the superior and posterior aspect of the calcaneus—that’s the insertion of the gastrocnemius, soleus, and plantaris of the posterior leg.
While we’re talking about pathologies, we know that stress fractures can occur in the feet; these happen most often in the second and third metatarsals. They get their name because these are typically caused by repeated stresses that weaken a bone to the point that it cracks. Why the second and third metatarsals? Those are usually the longest and thinnest, so the most vulnerable of the metatarsal group.
Common Questions about Ligaments and Joints of the Human Foot
At the hinge joint of the ankle is a set of ligaments collectively referred to as the deltoid ligament. This is because they fan out like a triangle from the medial malleolus of the tibia and attach to various tarsals.
Metatarsophalangeal joints are located between the heads of the five metatarsals and their proximal phalanges. These are condyloid joints in which the heads of the metatarsals are rounded and abut concave surfaces on the proximal phalanges. Condyloid or ellipsoidal joints allow more movement than simple hinge joints. As a result, at the metatarsophalangeal joints, we get not only flexion and extension, but abduction, adduction, and even a bit of circumduction.
The talus is said to have a head, neck, and cube-shaped body. While the body articulates with the tibia and fibula, the head faces anteriorly—or better said, distally. Some references indicate it as forming more or less a ball-and-socket joint with the concave surface of the boat-shaped navicular bone. Besides its role in ankle movements, the talus functions to transmit the standing weight of the body from the tibia to the other bones in the foot.
