Plantar fascia
Encyclopedia
The plantar fascia
is the thick connective tissue
which supports the arch
on the bottom of the foot
. It runs from the tuberosity of the calcaneus (heel bone) forward to the heads of the metatarsal bones
(the bone between each toe
and the bones of the mid foot).
The often painful condition plantar fasciitis
is an inflammatory condition of the plantar fascia.
The plantar fascia is a broad structure that spans between the medial calcaneal tubercle and the proximal phalanges
of the toes. There is still some debate as to whether it is deep fascia
or an aponeurosis
. The Dorland’s Medical Dictionary defines an aponeurosis as: (i) a white, flattened or ribbon-like tendinous expansion, serving mainly to connect a muscle with the parts that it moves, (ii) a term formerly applied to certain fasciae. Further, it defines the plantar aponeurosis as bands of fibrous connective tissue radiating toward the bases of the toes from the medial process of the tuber calcanei (posterior half of the calcaneus).
The plantar fascia is made up of predominantly longitudinally oriented collagen
fibers. There are three distinct structural components: the medial component, the central component (plantar aponeurosis), and the lateral component (see diagram at right). The central component is the largest and most prominent.
In younger people the plantar fascia is also intimately related to the Achilles tendon
, with a continuous fascial connection between the two from the distal aspect of the Achilles to the origin of the plantar fascia at the calcaneal tubercle. However, the continuity of this connection decreases with age to a point that in the elderly there are few, if any, connecting fibers. There are also distinct attachments of the plantar fascia and the Achilles tendon to the calcaneus so the two do not directly contact each other. Nevertheless, there is an indirect relationship whereby if the toes are dorsiflexed
, the plantar fascia tightens via the windlass
mechanism. If a tensile force is then generated in the Achilles tendon it will increase tensile strain in the plantar fascia. Clinically, this relationship has been used as a basis for treatment for plantar fasciitis, with stretches and night stretch splinting being applied to the gastrocnemius
/soleus muscle
unit.
The plantar fascia contributes to support of arch of the foot by acting as a tie-rod, where it undergoes tension when the foot bears weight. One biomechanical
model estimated it carries as much as 14% of the total load of the foot. In an experiment using cadaver
s, it was found that failure of the plantar fascia averaged at loads of 1189 ± 244 newtons (121 ± 24 kgf
or 267 ± 55 ft-lb). Interestingly, failure most often occurred at the proximal attachment to the calcaneus, which is consistent with the usual location of symptom
s (i.e. in plantar fasciitis). Complete rupture
or surgical release of the plantar fascia leads to a decrease in arch stiffness and a significant collapse of the longitudinal arch of the foot. By modeling it was predicted such conditions would result in a 17% increase in vertical displacement and a 15% increase in horizontal elongation of the foot when it was loaded at 683 newtons (153.5 lbf). Surgical release also significantly increases both stress in the plantar ligament
s and plantar pressures under the metatarsal heads. Although most of the figures mentioned above are from either cadaver
studies or investigations using models, they highlight the relatively large load the plantar fascia is subjected to while contributing to the structural integrity of the foot.
The plantar fascia also has an important role in dynamic function during gait
. It was found the plantar fascia continuously elongated during the contact phase of gait. It went through rapid elongation before and immediately after mid-stance, reaching a maximum of 9% to 12% elongation between mid-stance and toe-off. During this phase the plantar fascia behaves like a spring, which may assist in conserving energy. In addition, the plantar fascia has a critical role in normal mechanical function of the foot, contributing to the "windlass mechanism". When the toes are dorsiflexed in the propulsive phase of gait, the plantar fascia becomes tense, resulting in elevation of the longitudinal arch and shortening of the foot (see 3A). One can liken this mechanism to a cable being wound around the drum of a windlass (see 3B); the plantar fascia being the cable, the metatarsal head the drum, and the handle, the proximal phalanx
. Therefore, the plantar fascia has a number of roles, the most important of these including supporting the arch of the foot and contributing to the windlass mechanism.
Fascia
A fascia is a layer of fibrous tissue that permeates the human body. A fascia is a connective tissue that surrounds muscles, groups of muscles, blood vessels, and nerves, binding those structures together in much the same manner as plastic wrap can be used to hold the contents of sandwiches...
is the thick connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
which supports the arch
Arches of the foot
-External links:* * *...
on the bottom of the foot
Foot
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...
. It runs from the tuberosity of the calcaneus (heel bone) forward to the heads of the metatarsal bones
Metatarsus
The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...
(the bone between each toe
Toe
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of...
and the bones of the mid foot).
The often painful condition plantar fasciitis
Plantar fasciitis
Plantar fasciitis is a painful inflammatory process of the plantar fascia, the connective tissue on the sole of the foot.Longstanding cases of plantar fasciitis often demonstrate more degenerative changes than inflammatory changes, in which case they are termed plantar fasciosis. The suffix...
is an inflammatory condition of the plantar fascia.
Anatomy of the plantar fascia
Phalanx bones
In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.The phalanges do not have individual names...
of the toes. There is still some debate as to whether it is deep fascia
Fascia
A fascia is a layer of fibrous tissue that permeates the human body. A fascia is a connective tissue that surrounds muscles, groups of muscles, blood vessels, and nerves, binding those structures together in much the same manner as plastic wrap can be used to hold the contents of sandwiches...
or an aponeurosis
Aponeurosis
Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, are histologically similar to tendons, and are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...
. The Dorland’s Medical Dictionary defines an aponeurosis as: (i) a white, flattened or ribbon-like tendinous expansion, serving mainly to connect a muscle with the parts that it moves, (ii) a term formerly applied to certain fasciae. Further, it defines the plantar aponeurosis as bands of fibrous connective tissue radiating toward the bases of the toes from the medial process of the tuber calcanei (posterior half of the calcaneus).
The plantar fascia is made up of predominantly longitudinally oriented collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
fibers. There are three distinct structural components: the medial component, the central component (plantar aponeurosis), and the lateral component (see diagram at right). The central component is the largest and most prominent.
In younger people the plantar fascia is also intimately related to the Achilles tendon
Achilles tendon
The Achilles tendon , also known as the calcaneal tendon or the tendo calcaneus, is a tendon of the posterior leg. It serves to attach the plantaris, gastrocnemius and soleus muscles to the calcaneus bone.- Anatomy :The Achilles is the tendonous extension of 3 muscles in the lower leg:...
, with a continuous fascial connection between the two from the distal aspect of the Achilles to the origin of the plantar fascia at the calcaneal tubercle. However, the continuity of this connection decreases with age to a point that in the elderly there are few, if any, connecting fibers. There are also distinct attachments of the plantar fascia and the Achilles tendon to the calcaneus so the two do not directly contact each other. Nevertheless, there is an indirect relationship whereby if the toes are dorsiflexed
Dorsiflexion
Dorsiflexion is the movement which decreases the angle between the dorsum of the foot and the leg, so that the toes are brought closer to the shin. The movement moving in opposite directions is called plantarflexion...
, the plantar fascia tightens via the windlass
Windlass
The windlass is an apparatus for moving heavy weights. Typically, a windlass consists of a horizontal cylinder , which is rotated by the turn of a crank or belt...
mechanism. If a tensile force is then generated in the Achilles tendon it will increase tensile strain in the plantar fascia. Clinically, this relationship has been used as a basis for treatment for plantar fasciitis, with stretches and night stretch splinting being applied to the gastrocnemius
Gastrocnemius muscle
In humans, the gastrocnemius muscle is a very powerful superficial pennate muscle that is in the back part of the lower leg. It runs from its two heads just above the knee to the heel, and is involved in standing, walking, running and jumping. Along with the soleus muscle it forms the calf muscle...
/soleus muscle
Soleus muscle
- References :* Gray, Henry. Pick, T. Pickering, & Howden, Robert . Gray's Anatomy . New York: Barnes & Noble Books.- External links :...
unit.
Biomechanics of the plantar fascia
Biomechanics
Biomechanics is the application of mechanical principles to biological systems, such as humans, animals, plants, organs, and cells. Perhaps one of the best definitions was provided by Herbert Hatze in 1974: "Biomechanics is the study of the structure and function of biological systems by means of...
model estimated it carries as much as 14% of the total load of the foot. In an experiment using cadaver
Cadaver
A cadaver is a dead human body.Cadaver may also refer to:* Cadaver tomb, tomb featuring an effigy in the form of a decomposing body* Cadaver , a video game* cadaver A command-line WebDAV client for Unix....
s, it was found that failure of the plantar fascia averaged at loads of 1189 ± 244 newtons (121 ± 24 kgf
Kilogram-force
A kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field...
or 267 ± 55 ft-lb). Interestingly, failure most often occurred at the proximal attachment to the calcaneus, which is consistent with the usual location of symptom
Symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
s (i.e. in plantar fasciitis). Complete rupture
Rupture of membranes
Rupture of membranes or amniorrhexis is a term used during pregnancy to describe a rupture of the amniotic sac. Normally, or "spontaneously", it occurs at full term at the onset of, or during, labor...
or surgical release of the plantar fascia leads to a decrease in arch stiffness and a significant collapse of the longitudinal arch of the foot. By modeling it was predicted such conditions would result in a 17% increase in vertical displacement and a 15% increase in horizontal elongation of the foot when it was loaded at 683 newtons (153.5 lbf). Surgical release also significantly increases both stress in the plantar ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
s and plantar pressures under the metatarsal heads. Although most of the figures mentioned above are from either cadaver
Cadaver
A cadaver is a dead human body.Cadaver may also refer to:* Cadaver tomb, tomb featuring an effigy in the form of a decomposing body* Cadaver , a video game* cadaver A command-line WebDAV client for Unix....
studies or investigations using models, they highlight the relatively large load the plantar fascia is subjected to while contributing to the structural integrity of the foot.
The plantar fascia also has an important role in dynamic function during gait
Gait (human)
Human gait is the way locomotion is achieved using human limbs. Different gaits are characterized by differences in limb movement patterns, overall velocity, forces, kinetic and potential energy cycles, and changes in the contact with the surface .- Foot strike :One variable in different gaits is...
. It was found the plantar fascia continuously elongated during the contact phase of gait. It went through rapid elongation before and immediately after mid-stance, reaching a maximum of 9% to 12% elongation between mid-stance and toe-off. During this phase the plantar fascia behaves like a spring, which may assist in conserving energy. In addition, the plantar fascia has a critical role in normal mechanical function of the foot, contributing to the "windlass mechanism". When the toes are dorsiflexed in the propulsive phase of gait, the plantar fascia becomes tense, resulting in elevation of the longitudinal arch and shortening of the foot (see 3A). One can liken this mechanism to a cable being wound around the drum of a windlass (see 3B); the plantar fascia being the cable, the metatarsal head the drum, and the handle, the proximal phalanx
Proximal phalanges
Proximal phalanges are bones found in the limbs of most vertebrates. In humans, they are the bones at the base of a toe or finger, the prominent, knobby ends of which are often called the knuckles....
. Therefore, the plantar fascia has a number of roles, the most important of these including supporting the arch of the foot and contributing to the windlass mechanism.
Abnormal conditions
- Plantar fasciitisPlantar fasciitisPlantar fasciitis is a painful inflammatory process of the plantar fascia, the connective tissue on the sole of the foot.Longstanding cases of plantar fasciitis often demonstrate more degenerative changes than inflammatory changes, in which case they are termed plantar fasciosis. The suffix...
is an often painful inflammatory process of the plantar fascia.- Calcaneal spur (heel spur) is a small calcified bone extension (osteophyte) located on the inferior aspect of the calcaneus or on the back of the heel at the insertion of the Achilles tendon. The condition is typically a response to plantar fasciitis over a period of time. It may also be related to ankylosing spondylitisAnkylosing spondylitisAnkylosing spondylitis , previously known as Bekhterev's disease, Bekhterev syndrome, and Marie-Strümpell disease is a chronic inflammatory disease of the axial skeleton with variable involvement of peripheral joints and nonarticular structures...
, typically in children.
- Calcaneal spur (heel spur) is a small calcified bone extension (osteophyte) located on the inferior aspect of the calcaneus or on the back of the heel at the insertion of the Achilles tendon. The condition is typically a response to plantar fasciitis over a period of time. It may also be related to ankylosing spondylitis
- Plantar fibromatosis is a relatively uncommon non-malignant thickening of the plantar fasciitis.
- Psoriatic arthritisPsoriatic arthritisPsoriatic arthritis is a type of inflammatory arthritis that, according to the National Psoriasis Foundation, will develop in up to 30 percent of people who have the chronic skin condition psoriasis...
is a type of inflammatory arthritis that may affect the plantar fasciitis.
