Generality
The foot is the anatomical structure placed at the distal end of each lower limb of the human body.
Since it has an important supporting function for the whole human body, the most interesting anatomical aspect of the foot is certainly its skeletal structure. This includes the bones of the tarsus, the metatarsal bones and the phalanges constituting the toes.
In addition to the support function, the foot also plays a fundamental role in the locomotion mechanism.
Among the most frequent pathologies affecting the foot, bone fractures deserve special mention.
Definition
The foot is the distal end of each lower limb of the human body, composed of 5 fingers.
In an upright position, it is perpendicular to the thigh-knee-leg axis and projected towards a single direction: forward.
Anatomical meaning of proximal and distal
Proximal and distal are two terms with opposite meaning.
Proximal means "closer to the center of the body" or "closer to the point of origin". Referring to the femur, for example, it indicates the portion of this bone closest to the trunk.
Distal, on the other hand, means "farther from the center of the body" or "farther from the point of origin. Referred (always to the femur), for example, it indicates the portion of this bone furthest from the trunk (and closer to the knee joint).
Anatomy of the foot
The foot is a rather complex structure, in which there are 26 bones, 33 joints and more than a hundred muscles, tendons and ligaments .
For the support function that the foot performs, the anatomical aspect is certainly more important than its skeletal structure. Consequently, this article will focus primarily on the bones that make up the foot and, secondarily, on the joint, muscle, tendon, and ligament structures.
Concept of back and sole of the foot
The back of the foot is the upper region of the foot, which looks upwards.
The sole of the foot, on the other hand, is the lower region of the foot, which is facing downwards.
SKELETON OF THE FOOT: THE BONES
The anatomists divide the bones of the foot into three groups or categories: the tarsal bones, the metatarsal bones and the phalanges.
- The tarsal bones of the tarsal or tarsal group . Located just below the ankle joint, there are 7 irregularly shaped bony elements: the talo (or astragalus), the calcaneus, the navicular, the cuboid and the three cuneiforms (lateral, intermediate and medial).
The talo and the calcaneus represent the proximal bones of the tarsus and play a fundamental role in the formation of the ankle, that is the articulation that allows the dorsiflexion and the plantarflexion of the foot. In this case, the upper edge of the talo takes place inside the mortar, the concavity formed by the lower extremities of tibia and fibula. The calcaneus serves as an insertion point for a couple of fundamental ligaments (the tibio-calcaneal ligament and the calcaneo-fibular ligament).
The navicular is the intermediate bone of the tarsal group; it resides anteriorly to the talo, posteriorly to the three cuneiforms and laterally to the cuboid. It has a protuberance for the insertion of the posterior tibial tendon.
The cuboid and the three cuneiforms are the most distal bones of the tarsus. Similar to a cube, the cuboid occupies a lateral position (with respect to the three cuneiforms) and borders on the heel, posteriorly, and with the last two metatarsus, anteriorly. From the shape of a wedge, the three cuneiforms reside in front of the navicular bone and behind the first three metatarsals; the particular arrangement of the three cuneiforms allows the metatarsal bones to constitute the so-called transverse arch of the foot.
- Metatarsal bones or, more simply, metatarsals . Belonging to the category of long bones, they are altogether 5 elements.
In each metatarsal, three regions can be distinguished: a central region, identified with the term body; a proximal region, called the base; finally, a distal region, known as the head.
The base of the metatarsus borders on the bones of the tarsus: starting from the medial side of the foot, the first three metatarsals adhere to the three cuneiforms, while the last two metatarsal to the cuboid bone.
The head of each metatarsal adheres to the first phalanx of each toe.
Body, base and head each have 3 to 4 joints; these joint elements will be the topic of discussion in the chapter dedicated to the joints of the foot.
- The phalanges . There are a total of 14 and they represent (as one could guess from a previous statement) the bony elements that make up the toes.
Except the first finger - the only one formed by 2 phalanges - all the other fingers have 3 phalanges each.
The phalanges closest to the head of the metatarsals (proximal phalanges) are called first phalanges; starting from these, the following are called second phalanges and third phalanges (NB: in the first finger, the numbering ends with the second phalanges).
Hindfoot, midfoot and forefoot: what do they mean and which bones of the foot do they include?
Anatomy experts have established that three zones can be recognized in the foot: the hindfoot area, the midfoot area and the forefoot area.
The area of the hindfoot is the most proximal part of the foot and includes the talus and calcaneus.
The midfoot area is the middle part of the foot (the prefix meso- means "in the middle") and includes the cuboid bone, the three cuneiforms and the navicular bone.
Finally, the forefoot area is the most distal part of the foot and includes the 5 metatarsals and phalanges of the toes.
FOOT JOINTS
To simplify the description of the numerous articulations of the foot, it was decided to divide them by bone sectors: the joints of the tarsal bones, the joints of the metatarsal bones and the joints of the phalanges .
At the tarsal level, 4 joints are relevant:
- The ankle (or talocrural joint ), which represents the most important joint element of the foot.
- The subtalar joint, which is the result of the synergy between talo and calcaneus.
- The talonavicular joint, which results from the union of talo and navicular bone.
- The calcaneocuboid joint, which is the result of the relationship between calcaneus and cuboid bone.
Going into more detail:
- The joints between metatarsals and tarsal bones are called tarso-metatarsal joints . These combine the base of the metatarsals with the cuneiform bones (metatarsal bones of the first three fingers) and the cuboid bone (metatarsal bones of the last two fingers).
- The joints between metatarsal and metatarsal are known as intermetatarsal joints . These connect two adjacent metatarsals; they are 3 in the metatarsal of the first and last toes, while they are 4 in the metatarsus of the second, third and fourth toes.
- The joints between metatarsals and the first phalanx are known as metatarsophalangeal joints . These stabilize the head of the metatarsals with the nearest phalanx, the proximal one.
At the phalangeal level, the joints that the phalanges form between them stand out, namely:
- The joint that links the first phalanx to the second phalanx, also known as the proximal interphalangeal joint .
- The joint that binds the second phalanx to the third phalanx, whose specific name is distal phalangeal joint .
This joint element is absent only in the first toe (the one that, vulgarly, is indicated by the term toe).
FOOT LINKS
A ligament is a formation of fibrous connective tissue, which connects two bones or two parts of the same bone.
The most important ligaments of the feet are: the plantar fascia, the calcareous-navicular plantar ligament and the calcaneo-cuboid ligament .
The plantar fascia is a long ligament, located on the lower edge of the foot (plant), which runs from the heel bones (calcaneus) to the finger bones. Morphologically similar to an arch, it allows the curvature of the foot and acts as a cushion that absorbs the shocks of walking, running, etc.
The plantar calcaneo-navicular ligament is the ligamentous element, located on the inferior margin of the foot, which goes from the calcaneus to the navicular bone. Functionally, it serves to support the head of the talus.
The plantar calcaneo-cuboid ligament is the ligament that runs from the calcaneus to the cuboid bone; its function is to help the plantar fascia during curvature.
Within this framework, we must not forget the existence of ankle ligaments, which are divided into two categories: the medial and the lateral.
The medial ligaments of the ankle are a total of 4, while the lateral ones are altogether 3.
FOOT MUSCLES
The good functionality of the foot depends on numerous muscles, some of which reside, at least in part, outside the foot itself.
For this reason, anatomy experts have decided to distinguish the muscular elements of the foot in two categories: the extrinsic muscles - which are tied, on the one hand, to a bone of the leg and, on the other side, to a bone of the foot - and the intrinsic muscles - which take place totally on the foot.
The main representatives of the extrinsic muscles are:
- The posterior tibial muscle
- The tibialis anterior muscle
- The long peroneal muscle
- The short peroneal muscle
- Twin muscles (or gastrocnemius)
- The soleus muscle
* Please note: twins and soleus together form the calf muscles, also known by the singular term triceps sura.
As for the intrinsic muscles, it should be pointed out that these, in turn, can be divided into two categories: the dorsals and the orthotics .
The intrinsic dorsal muscles are the extensor short muscle of the big toe and the short extensor muscles of the toes.
The intrinsic plantar muscles, however, are:
- The medial plantar muscles, also called the muscles of the first finger (or big toe)
- Big-tooth abductor muscle
- Short flexor muscle of the big toe
- Adductor muscle of the big toe
- The lateral plantar muscles, also called the 5th finger muscles
- 5th abductor muscle of the toe
- Short flexor muscle of the 5th toe
- Adductor muscle of the 5th toe
- Intermediate plantar muscles
- Short flexor muscle of the central toes of the foot
- Square muscle of the sole of the foot
- Lumbrical muscles (four in all)
- Interosseous muscles (seven in total)
In general - although it is necessary to specify that each foot muscle covers a specific function - the intrinsic dorsal muscles and the intrinsic plantar muscles guarantee, respectively, the dorsiflexion and the plantarflexion of the foot.
What do the terms dorsiflexion and plantarflexion mean?
Dorsiflexion and plantarflexion are two opposite gestures.
Dorsiflexion is the movement that allows you to point your foot on the floor and walk on the toes; plantarflexion, on the other hand, is the movement that allows you to lift your foot and walk on your heels.
For the correct execution of dorsiflexion, the twins, the soleus and the posterior tibial muscle are also fundamental; while, for the proper execution of plantarflexion, the contribution of the anterior tibial muscle is also essential.
TENDINI OF THE FOOT
A tendon is a structurally very similar formation to a ligament, with the only difference joining a muscle to a bone element (NB: the ligament unites two generally distinct bone elements).
The tendons of the foot are numerous, as, as the reader will surely have noticed, there are many foot muscles (or in any case involved in its movement).
The most important tendon of the foot - both for the volume it occupies and for the clinical aspect it covers - is the Achilles tendon . This tendon structure connects the calf muscles (the twins and the soleus) to the heel. It is essential for walking, running and jumping. Its break severely limits a person's motor skills and requires reconstructive surgery.
Functions
The foot covers various functions:
- Ensures stability in standing position;
- Absorbs much of the body's weight;
- Allows locomotion. Thanks to its complex anatomy, the foot allows man to walk, run, jump and walk on uneven surfaces.
Foot Diseases
The most common problems that can affect the foot are the fractures of the bones that constitute it, in this case: the fracture of the talus, the fracture of the calcaneus, the fracture of a metatarsal and the fracture of a phalanx .
ASTRAGALUS FRACTURE
The fractures of the astragalus (or talo) may be located in two distinct points of this bone: on the so-called neck or on the so-called body .
Typically, fractures of the neck of the talus follow an excessive dorsiflexion of the foot. This movement causes the talus to press, in an abnormal and violent manner, against the tibia, breaking due to the impact. Upon occurrence, these types of ruptures can alter direct blood flow to the talus and lead to the onset of osteonecrosis (or avascular necrosis ).
The fractures of the talo's body are, very often, the result of jumps carried out from an excessive height.
FRACTURE OF THE CALCIUM
Usually, fractures of the calcaneus are due to impacts that affect the heel and push the heel against the astragal in a very violent manner.
The main circumstances that cause a heel fracture are falls on the heels.
The fractures of the calcaneus are conditions capable of causing various late complications, on all arthritis against the subtalar joint and severe pain during the movements of eversion and inversion of the foot.
FRACTURE OF A METATARSUS
At least three particular events can cause the fracture of one or more metatarsals:
- A violent blow, directed at the foot. This is the case, for example, of a heavy object falling on the foot.
Metatarsal fractures due to violent impacts are the most common.
- A stress factor that affects the foot in general or a part of it in particular. This type of fracture is called metatarsal stress fracture and mainly affects the metatarsals of the 2nd, 3rd and 4th finger. It is very common among good athletes and is generally a microfracture .
- Excessive foot inversion. With a violent and very marked inversion of the foot, the short peroneal muscle could "pull" the metatarsal of the 5th finger and cause its rupture.
Figure: eversion and inversion movements of the foot.
The treatment of metatarsal fractures varies depending on the site of the bone rupture and whether the latter is composed or decomposed.
In fact, in certain cases, rest and immobilization of the lower limb could suffice; in others, on the other hand, it may be necessary to have surgery to weld the bone fracture.
FRACTURE OF A FALANGE
Fractures of one or more phalanges are conditions of slight gravity, which arise as a result of traumatic events that damage the foot. Generally, they only require a rest period of 20-30 days.
