Anatomy And Physiology

Anatomy Physiology

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The human ankle is an amazing work of engineering. Yes, it acts like a hinge joint, but it is so much more. A person can also rotate their ankle in many directions. Because it has to withstand 1.5 times your body weight when you walk and up to 8 times you weight when you run, it must be very stable, as well as able to move smoothly. The eOrthopod site gives a detailed description of the combination of bones, ligaments and tendons that make up the ankle.

The Orthopod article, states:

“The ankle joint is formed by the connection of three bones. The ankle bone is called the talus. The top of the talus fits inside a socket that is formed by the lower end of the tibia (shinbone) and the fibula (the small bone of the lower leg). The bottom of the talus sits on the heelbone, called the calcaneus.”

“The talus works like an inside the socket to allow your foot to move up (dorsiflexion) and down (plantarflexion).”

They compare the ankle joint to a technique used by craftsmen and woodworkers when they are creating a strong structure: a mortise and tenon joint. This is a woodworking process where the wood is joined, by alternate, interlocking wedge shapes to create a stable joining between two separate sections of wood.

The ankle bone is the talus. It fits inside a socket that is formed by the lower end of the tibia or shinbone and the fibula, the smaller bone of the lower leg. That is the mortise connection. The bottom of the talus sits on the calcaneus or heelbone.

If all of this were just sitting freely in place, it would not be a very stable connection. The wood mortise and tenon joint uses glue, and the joint is solid but non-moving. The ankle is a very flexible joint, so the body uses ligaments and tendons to keep it in place and make it stable.

The Protective Covering

Another important aspect of this joint is not only the structure and coming together of the various bones, but the protective covering of the bones. They are covered with a slick material called articular cartilage. This is what allows the bones to move smoothly against one another in all the human joints. When this articular cartilage wears down or is damaged, that is when a person feels pain in that joint.

How the Ankle is Held Together

The Southern California Orthopedic Institute gives a good description of how the ligaments connect and hold the bones into position, yet allow its flexibility.

“The ankle is a complex mechanism. What we normally think of as the ankle is actually made up of two joints: the subtalar joint, and the true ankle joint. The true ankle joint is composed of 3 bones, the tibia which forms the inside, or medial, portion of the ankle; the fibula which forms the lateral, or outside portion of the ankle; and the talus underneath. The true ankle joint is responsible for up and down motion of the foot.”

“Beneath the true ankle joint is the second part of the ankle, the subtalar joint, which consists of the talus on top and calcaneus on the bottom. The subtalar joint allows side to side motion of the foot.”

“The ends of the bones in these joints are covered by articular cartilage (1). The major ligaments of the ankle are: the anterior tibiofibular ligament (2), which connects the tibia to the fibula; the lateral collateral ligaments (3), which attach the fibula to the calcaneus and gives the ankle lateral stability; and, on the medial side of the ankle, the deltoid ligaments (4), which connect the tibia to the talus and calcaneus and provide medial stability.”

“These components of your ankle, along with the muscles and tendons of your lower leg, work together to handle the stress your ankle receives as you walk, run and jump.”

Ligaments and Tendons

Now to describe in some detail what ligaments and tendons are so you can understand how they function. They are soft tissues, made up of fibers, which are made of a material called collagen. These fibers are bundled in a rope-like fashion. Like rope, they come in many different sizes and are made of many smaller fibers. Their thickness determines their strength. The difference between ligaments and tendons is that tendons attach muscle to bones.

How all the various tendons and ligaments are joined within and around the ankle joint is quite involved. For a complete description you can visit this link on and read the full setup as well as see detailed images of the whole ankle joint.

The ligaments that surround the ankle enclose it in a watertight sac called the joint capsule.  Many nearby tendons support it, the most well known tendon is the Achilles tendon that is used for running, walking and jumping. This tendon attaches the calf muscles to the calcaneus or heelbone. It also allows us to rise up on our toes. If you look at any anatomy drawings of the ankle you would see that the ligaments and tendons are interlaced in position to allow the best function of the ankle. What seems surprising—is that the motion of the ankle is caused by the stronger muscles in the lower leg, whose tendons actually pass by the ankle—connecting in the foot!

A Listing of the Bones and Tendons

Below are lists of the various bones and ligaments that make up the ankle joint, found on the Center for Holistic Instruction, a website for massage therapists. Hopefully this list format will help you put it all together.

1.  Talocrural Joint: This is a hinge joint formed by the distal ends of the fibula and tibula that enclose the upper surface of the talus. It allows for both dorsiflexion (decreasing the angle between the foot and the shin) and plantarflexion (increasing the angle).

2.  Inferior tibiofibular Joint: This is strong joint between the lower surfaces of the tibia and fibula. This is supported by the inferior tibiofibular ligament.

3.  Subtalar Joint: This joint comprises of the articulating surfaces of the talus and the calcaneus. It provides shock absorption and the movements of inversion and eversion (inward and outward ankle movements respectively) occur here.”

 The Ligaments are Listed Here:

 A.   Lateral Collateral Ligament:

 The lateral collateral ligament prevents excessive inversion. It is considerably weaker than the larger medial ligament and thus sprains to the lateral ligament are much more common. It is made up of 3 individual bands:

1.  Anterior talofibular ligament (AFTL): passes from the fibula to the front of the talus bone.

2.  Calcaneofibular ligament (CFL)- connects the calcaneus and the fibula

3.  Posterior talofibular Ligament (PTFL)- passes from the back of the fibula to the rear surface of the calcaneus.

B.  Medial Collateral Ligament:

 "The medial ligament also known as the deltoid ligament is considerably thicker than the lateral ligament and spreads out in a fan shape to cover the distal (bottom) end of the tibia and the inner surfaces of the talus, navicular, and calcaneus," as stated on the site, Center for Holistic Instruction.

The anatomy of the human body is incredible. It is indeed an intricate machine that if taken care of properly, can function in amazing ways for a long time.

More about this author: Barbara Zarrella

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