Welcome to Denton Foot and Ankle Surgery Specialists

May 1, 2020

Foot Care

Biomechanics

It took me a long while to decide what my first blog post would be about. I mean, I have never written a blog and really did not know where to start. First and foremost, I wanted to once again thank you all for allowing me to care for your foot conditions and treat your pain. I would be unable to do what I love without you as my patients. There are so many subjects about the foot I just love and could discuss for hours on end. But what would I consider one of the most important subjects to inform my patients on? Biomechanics. In podiatry, biomechanics is a study to determine the movement of the ankle, toes, and the foot, as well as the forces that impact them. We train in this specialty in order to effectively diagnose and treat conditions that affect people’s everyday movement.

What would I consider one of the most important subjects to inform my patients on? Biomechanics.

Most disorders we see in the foot can be retraced back to an abnormal biomechanical function. Before we can discuss how foot deformities and foot pain are connected to poor biomechanics it would be helpful to understand normal biomechanics. And it just so happens to be one of my favorite subjects. Normal biomechanics minimizes energy expenditure and reduces stress on the bones, joints, and soft tissues of the lower extremities. Abnormal biomechanics contribute to most of the clinical problems affecting the foot and ankle. Movement of the foot and ankle is a complex action involving many joints and it can get quite complicated, so I am going to do my best to do a good overview of the subject without getting too medical.

The foot is made of 26 bones and 33 joints. There are two more bones that make up the ankle joint. So, the ankle and foot combined have 28 bones and 35 joints. They all have a purpose and a normal function. The ankle is made up of the tibia, fibula and the talus, this joint allows for the up and down motion of the ankle. What we call the hindfoot is made up of the calcaneus (known as the heel bone) and the talus (known as the ankle bone). The ankle joint includes the tibia, the fibula and the talus. There is a joint above the ankle joint known as the syndesmotic joint, this is a joint that is between just the tibia and the fibula. The next joint down is the subtalar joint. This joint is made between the talus and the calcaneus and sits under the ankle joint. This joint contributes to a complex set of motions known as pronation and supination. The next set of bones in the foot are known as the midfoot. The midfoot consists of the navicular, the cuboid and three wedge shaped bones known as the cuneiform bones. The midtarsal joint consists of the talus and navicular as well as the calcaneus and cuboid. The next set of bones in the foot are known as the forefoot. This includes five metatarsal bones and the phalanges (the toe bones). The metatarsals are a part of the Lisfranc joint. This joint is made up of the five metatarsals, the cuneiform bones and the cuboid. The five metatarsals then join the toe bones at the metatarsal phalangeal joint. There are then three bones in each toe and two joints, except the big toe, which only has two bones and one joint. There are two small bones under the head of the first metatarsal known as sesamoid bones. Again, all these bones and joints have a normal shape, position and function. When you, as the patient, start to feel pain in your foot it is usually due to one or more of the bones or joints having an abnormal shape or abnormal function.

When it comes to discussing motion in the foot there are special definitions that we use. There are what are called planes of motion. There are three different plans of motion. One plane is called the sagittal plane. In this plane we see up and down motion. Another plane of motion is called the transverse plane, in this plane we see motion called adduction and abduction. The adduction motion is motion of the foot or toes moving inward, or towards the other foot and abduction is motion where the foot or toes is moving outward away from the other foot. The last plane of motion is called frontal plane this is where motion that occurs in this plain is called eversion and inversion. This is the in and out motion of the foot. The foot moves in all three of these planes, so it is considered to have triplane motion. When you add all three planes together the foot moves in a pronation and supination type of motion. Both supination and pronation are necessary for good foot biomechanics. The main function of pronation, in the foot at initial ground contact is to absorb impact and adapt to the ground. During lift-off is when supination is critical, and the foot is converted from a flexible to a rigid structure by both passive and active mechanisms. When these mechanisms in the foot fail to function properly, the relationship of the foot to the ground is altered, which increases stress on one or more of the joints in the foot and ankle, leg, or pelvis. Pronation is necessary in order to provide good shock absorption at heel strike. Supination is necessary for a good propulsive gait. A person who has a higher arch has more supination a person who has a lower arch has more pronation.

We start to see pathology occur in the foot when you have too much motion in any plane. So, you could have too much eversion which often leads to a more pronated or flat foot. You could have too much inversion and that often leads to a more supinated or high arch foot.

Understanding foot biomechanics can help improve movement and eliminate pain, stopping further stress to the foot. Your foot doctor should perform a comprehensive biomechanical exam to understand your deformity in detail so that you together with your doctor can decide the best course of treatment for your disorder. If you believe you have any of these disorders please reach out to us, I would love to help. Also, click the link below to see the explanation video portion of this blog entry.

– Dr. Lesley Richey Smith, DPM

+ Click To See The Video

By bennrichey

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