Before looking at the functions of specific muscles and soft tissue structures of the feet and ankles, the main elements of the musculoskeletal system will be explained along with an overview of how these things work together in unison to create and control movement.
At birth humans have about 300 bones in their body. As people grow, some of these bones, such as those in the head, pelvis and sacrum, fuse together. As a result, adults end up with approximately 206 bones in their body. As mentioned previously, your feet alone contain 52 bones. These bones provide the framework for the structures of the feet and ankle (Dimon, 2008). They also protect nerves, and together with muscles and fascia enable us to move.
The word ligament comes from the Latin word “ligare” which means to “bind or tie.” Ligaments are a tough band of connective tissue that joins bones together at a joint (see Figure 11). Ligaments provide stability to the feet and ankles by keeping bones together and preventing excessive movement (Dimon, 2008).
Figure 11: Ligaments of the Foot and Ankle
Muscles are specialized tissues made up from bundles of cells responsible for creating movement in the feet and ankles by either contracting or expanding (see Figure 12). The adult human body contains over 650 named skeletal muscles. Examples of muscles found in the feet and ankles would be the soleus, the tibialis anterior, and the peroneals (See Figure 12 & 13) (Dimon, 2008).
Figure 12: Examples of Muscles in the Foot
The word tendon comes from the Latin word “tendere” which means “to stretch.” Tendons are flexible, yet tough connective tissues that help attach muscle to bone (see Figure 6). A tendon is formed as the muscle fibers come together at one end (similar in nature to bunching a group of rose stems together at the bottom) (Price & Bratcher, 2010). This tapering of the muscle enables it to attach, via the tendon, to the appropriate site on a bone. One of the most widely known in important tendons in the foot/ankle complex is the Achilles tendon (see Figure 13).
Figure 13: Illustration of the Achilles Tendon
Muscles can produce a lot of power, so the tendon must be rigid, but also flexible enough to make sure that it does not detach from the bone when the muscle contracts. For example, if a person ruptures his or her Achilles tendon this means that the tendon has torn away from its attachment site on the back of the calcaneus. Excessive wear and tear on a tendon can cause it to become inflamed, a condition which is referred to as tendonitis.
Fascia is a three-dimensional web of tissue that connects all the soft tissues in the body (see Figure 14). There are two levels of fascia in the body. The first level is called the superficial fascia. It lies near the surface of the body and helps bind our skin to the tissues underneath. The second layer is called deep fascia. It helps bind together different layers of a muscle and also ensheathes the nerves and blood vessels and organs (Myers, 2008).
In order to get a better idea of what fascia is and what it does, imagine a time when you tried to take the skin off a chicken or turkey breast. The skin would have been attached by a thin film to the muscle underneath. That thin film was the superficial fascia. When you tried to remove the meat from the drumstick or leg, you would have noticed another thin membrane that wrapped around bunches of muscle fibers and then to the bone. That membrane was the deep fascia.
Figure 14: Example of Fascia of the Foot
Fascia is one of the most important, but also one of the most overlooked elements of a healthy musculoskeletal system. Since fascia is interconnected and wrapped around every single part of our body, any restrictions or irritations in the fascial layers or systems can affect the functioning of structures in that immediate area as well as in other areas of the body. Because of the many bones, ligaments, tendons, nerves and other soft tissue structures that are enveloped by fascia in the feet and ankles it is very important to understand the anatomy of the individual muscles of the foot and ankle area, especially where they originate and insert. This will help you follow the network of muscles up from the feet to the lower leg and beyond to gain a better understanding of how muscles work together as a chain covered in fascia affecting function of the entire body (Rolf, 1989).
Our “Bungee Cord” System of Muscles
Now that you have a good understanding of the individual components of the feet and ankles and the structures that make up the musculoskeletal system, it is important to understand how these systems work together in real life with motion and gravity added. As discussed previously, most anatomical texts describe the primary function of a muscle as having the ability to pull two bones toward each other. However, in real life our muscles don’t always work this way. Instead, our muscles tend to work in a fashion similar to a bungee cord in that tension increases as the fibers elongate, simultaneously slowing down force and storing potential energy for use when the fibers need to contract.
In order to better appreciate how the musculoskeletal system is akin to a bungee cord system, visualize a person who is attached by his ankles to the end of a bungee cord as he is about to jump off a bridge. If the bungee cord gets the right amount of tension on it as the person nears the ground, then he will be saved from smashing into the earth. However, if the bungee cord does not pull tight at the right time, the person will impact the ground with dire consequences. The muscles, tendons, ligaments, and fascia of our bodies act in a similar way to bungee cords. If these bungee cords work together, they can protect our musculoskeletal structures (especially the joints) from excessive stress by pulling tight at the right moment to help slow down force through the body as the feet and ankles interact with the ground (see Figure 15).
Figure 15: Bungee Cord Illustration of How Muscles Work
The bungee cord characteristic of the musculoskeletal system also enables muscles to store energy that can be used to create strong, powerful movements as this energy is released (i.e., when the muscle fibers contract). This is similar to when the bungee cord reaches its maximum stretch, it then pulls the person powerfully back up to where the bungee cord is anchored. This stored energy is particularly important to achieve correct function of the feet and ankles as it enables a powerful push off when walking, running, jumping, etc.