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Basic Foot Anatomy
The foot is made up of 26 bones, which are divided into three sections called the rearfoot, midfoot and forefoot. The talus and calcaneus (heel bone) are the bones that make up the rearfoot. The talus is the highest bone in the foot and it is also part of the ankle. The calcaneus is the largest bone in the foot. It sits below the talus. The navicular, cuboid and the three cuneiforms are the bones that make up the midfoot. The five metatarsals and nine phalanges are the bones that make up the forefoot.

There are three arches in the foot. There is an inner (medial) arch, an outer (lateral) arch and an arch in the forefoot called the transverse arch. Ligaments are like strong ropes that connect bones and provide stability to joints. In the foot there are numerous ligaments that support the arches and stabilize the bones. These ligaments are located on the top (dorsal), bottom (plantar) medial and lateral aspects of the foot.

The plantar fascia is a key structure that helps support the medial and lateral arches of the foot. The plantar fascia is a strong connective tissue that runs along the bottom of the foot connecting the heel to the base of the toes. When weight is put on the foot the plantar fascia helps to "lock" the bones of the foot and stabilizes these arches.

Many of the muscles that move the foot originate from the lower leg. These muscles attach via tendons to various bones in the foot. The muscles that move the foot upwards (dorsiflex the foot) originate on the front of the lower leg. The muscles that move the foot outwards (evert the foot) originate on the lateral aspect of the lower leg. The muscles that move the foot inwards (invert the foot) originate deep on the back of the lower leg. The muscles that move the foot downwards (plantarflex the foot) and propel the body forward originate from the knee and the back of the lower leg. The muscles that play the largest role in propulsion are the calf muscles (gastrocnemius and soleus muscles). These muscles join to form the Achilles tendon that attaches onto the calcaneus. In addition to the long muscles, there are also numerous short muscles in the foot. These muscles also play a role in stabilizing the arches of the foot and in moving the toes.

Finally, there are numerous fat pads located on the bottom of the foot. These fat pads act as "cushions" or "shock absorbers". The largest fat pad in the foot is located in the heel directly below the calcaneus. There are other "cushions" or "shock absorbers" in the foot called bursae. A bursa (pl. bursae) is a small fluid filled sac that also decreases the friction between two tissues and protects bony structures. There are many different bursae around the foot. One that is commonly injured is the bursa at the back of the calcaneus called the superficial calcaneal bursa. Normally, a bursa has very little fluid in it but if it becomes irritated it can fill with fluid.

Basic Ankle Anatomy
This section is a review of basic ankle anatomy. It covers the bones, ligaments, muscles and other structures that make up the ankle. For more information on how the ankle works please read the section on basic foot and ankle biomechanics.

The ankle is made up of three bones, which are connected by muscles ligaments and tendons. The tibia is the large bone located on the inner (medial) aspect of the shin. The fibula is the smaller bone located on the outer (lateral) aspect of the shin. The ends of the tibia and fibula are joined together by a strong ligament to form a socket called the ankle "mortis". The talus is the highest bone of the foot. It has a "dome" which fits inside the ankle mortis to form the ankle joint. The ankle links the foot to the lower leg. The bony structure on the lateral aspect of the ankle is called the lateral malleolus. It is formed by the end of the fibula. The bony structure on the medial part of the ankle is called the medial malleolus. It is formed by the end of the tibia. The medial and lateral malleoli are the bony attachment sites for the ankle ligaments.

Articular cartilage is a smooth shiny material that covers the ends of the bones in the ankle. There is articular cartilage anywhere that two bony surfaces come into contact with each other. In the ankle, articular cartilage covers the end of the tibia, the dome of the talus and a small part of the fibula. Articular cartilage allows the ankle bones to move easily as the ankle bends up (dorsiflexes), and bends down (plantarflexes).

Ligaments are like strong ropes that help connect bones and provide stability to joints. In the ankle there are three ligaments on the lateral aspect of the ankle and one broad ligament on the medial aspect of the ankle. It is most common for people to injure the ligaments on the lateral aspect of the ankle.

Tendons connect muscles to bone. Many of the muscles that move the foot originate from the lower leg. The tendons of these muscles cross the ankle and attach to various bones in the foot. The muscles that move the foot upwards (dorsiflex the foot) originate on the front of the lower leg. The muscles that move the foot outwards (evert the foot) originate on the lateral aspect of the lower leg. The muscles that move the foot inwards (invert the foot) originate deep on the back of the lower leg. The muscles that move the foot downwards (plantarflex the foot) and propel the body forward originate from the knee and the back of the lower leg. The muscles that play the largest role in propulsion are the calf muscles (gastrocnemius and soleus muscles). These muscles join to form the Achilles tendon that attaches onto the heel bone (calcaneus).

Finally, a bursa (pl. bursae) is a small fluid filled sac that decreases the friction between two tissues and protects bony structures. There are many different bursae around the ankle. The two that are commonly injured are the bursae that protect the medial and lateral malleoli. Normally, a bursa has very little fluid in it but if it becomes irritated it can fill with fluid.

Basic Foot & Ankle Biomechanics
Biomechanics is the term used to describe movement of the body. This section is a review of basic foot and ankle biomechanics. In order to understand the biomechanics of the foot and ankle it is important to understand their anatomy. Please read the sections on basic foot anatomy and basic ankle anatomy before reading this section.

The ankle is a modified hinge joint. It plays a key role in transferring the forces from the foot to the leg. The ankle joint is made up of three bones, which are connected by ligaments, muscles and tendons. A strong ligament joins the ends of the tibia and fibula to form the ankle "mortis". The "dome" of the talus (the highest bone of the foot) fits inside the ankle mortis to form the ankle joint. The ankle allows movement in only one plane. It allows the foot to move upwards (dorsiflexion) and downwards (plantar flexion).

The foot is made up of 26 bones. There are numerous joints between these bones that allow the foot to be both a rigid lever and a shock absorber. The largest joint in the foot is the subtalar joint. Inward movement of the foot (inversion), and outward movement of the foot (eversion) occur primarily at the subtalar joint.

The normal end ranges of motion for the foot and ankle vary between individuals and between children and adults. The following are approximate end ranges of motion for adults:

Dorsiflexion - 20 degrees
Plantar flexion - 60 degrees
Eversion - 15 degrees
Inversion - 35 degrees

The gait cycle (walk cycle) describes what happens to the foot and ankle from the point of initial contact of one foot with the ground to the point at which the same foot contacts the ground again. The gait cycle is divided into the swing phase and the stance phase. During the swing phase the foot is not in contact with the ground. As the name implies it is the phase of the gait cycle in which the foot swings forward to take another step. During the stance phase the foot is in contact with the ground. The stance phase of the gait cycle can also be divided into three stages. The first stage is called heel strike, the second stage is called mid-stance, and heel lift is the final stage. The biomechanics of the foot are best explained by describing what happens to the foot during the stance phase of the gait cycle.

During heel strike of the stance phase the foot begins to pronate. Pronation of the foot is the term that describes the rolling motion of the foot inwards and flattening of the inner (medial) arch of the foot. Pronation allows the foot to adapt to uneven terrain and absorb the impact of the foot striking the ground. It is during this phase that the foot begins to act like a shock absorber.

During midstance the entire foot is in contact with the ground and the weight of the body is directly over the foot. It is during this phase that the foot is maximally pronated. The foot acts as a shock absorber during the early part of this phase. As the body weight shifts forward the foot begins to return to a neutral position in preparation for heel lift.

Heel lift occurs at the end of the stance phase. Supination of the foot is the term used to describe the rolling motion of the foot outwards and the rising of the inner (medial) arch of the foot. During heel lift, the foot supinates to act as a rigid lever. The plantar fascia is a strong connective tissue that runs along the bottom of the foot connecting the heel to the base of the toes. The bones, muscles and the plantar fascia act together to form this rigid lever.

Abnormal amounts of pronation or supination can cause a variety of foot and leg problems. Abnormal pronation (overpronation) occurs as a result of the foot pronating when it should be neutral or supinating. Abnormal supination occurs when the foot is too rigid. These abnormal biomechanics can create lower back, hip, knee, ankle and/or foot problems.