Foot and Ankle Structure and Function: Difference between revisions
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| {{#ev:youtube|0R4zRSE_-40|400}} | | {{#ev:youtube|0R4zRSE_-40|400}}<ref> Dr Glass DPM. Ankle & Subtalar Joint Motion Function Explained Biomechanic of the Foot - Pronation & Supination. Published 21 January 2008. Avalaible from https://www.youtube.com/watch?v=0R4zRSE_-40&t=29s. (last accessed 10 June 2019) | ||
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Revision as of 11:02, 10 June 2019
Original Editor - Vinit Kothekar
Top Contributors - Vinit Kothekar, Wanda van Niekerk, Kim Jackson, Admin, Evan Thomas, Lucinda hampton, Chelsea Mclene, Candace Goh, Rachael Lowe, Simisola Ajeyalemi, WikiSysop, Rucha Gadgil, Jess Bell, Khloud Shreif, 127.0.0.1, Ewa Jaraczewska, Cath Young and Priyanka Chugh
Anatomy[edit | edit source]
The foot and ankle form a complex system which consists of 28 bones, 33 joints, 112 ligaments, controlled by 13 extrinsic and 21 intrinsic muscles. The foot is subdivided into the rearfoot, midfoot, and forefoot. It functions as a rigid structure for weight bearing and it can also function as a flexible structure to conform to uneven terrain. The foot and ankle provide various important functions which includes:
- supporting body weight,
- providing balance,
- shock absorption,
- transferring ground reaction forces,
- compensating for proximal malalignment,
- and substituting hand function in individuals with upper extremity amputation/paralysis.[1]
[2] | [3] |
Talocrural (TC) Joint[edit | edit source]
The talocrural joint is formed between the distal tibia-fibula and the talus, and is commonly known as the ankle joint. The distal and inferior aspect of the tibia – known as the plafond – is connected to the fibula via tibiofibular ligaments forming a strong mortise which articulates with the talar dome distally. It is a hinge joint and allows for dorsiflexion and plantarflexion movements in the sagittal plane.
Subtalar (ST) Joint[edit | edit source]
It is also known as the talocalcaneal joint and is formed between the talus and calcaneus. The talus has three facets (anterior, middle and posterior) which articulate inferiorly with the calcaneus.
Midtarsal (MT) Joint[edit | edit source]
Also known as transverse tarsal joints or Chopart’s joint. It is an S-shaped joint when viewed from above and consists of two joints – the talonavicular joint and calcaneocuboid joint.
- Talonavicular (TN) Joint - Formed between the anterior talar head and the concavity on the navicular. It does not have its own capsule, but rather shares one with the two anterior talocalcaneal articulations.
- Calcaneocuboid (CC) Joint - Formed between the anterior facet of the calcaneus and the posterior cuboid. Both articulating surfaces present a convex and concave surface, with the joint being convex vertically and concave transversely. Very little movement occurs at this joint.
Tarsometatarsal (TMT) Joint Complex[edit | edit source]
Also known as Lisfranc’s joint. The distal tarsal rows including the three cuneiform bones and cuboid articulate with the base of each metatarsal to form the TMT complex. It is an S-shaped joint and is divided into 3 distinct columns[1]:
- Medial – composed of 1st metatarsal and medial cuneiform
- Middle – composed of 2nd and 3rd metatarsals and intermediate and lateral cuneiforms, respectively
- Lateral – composed of 4th and 5th metatarsals and the cuboid; it also divides the midfoot from forefoot
Metatarsophalangeal (MTP) Joints and Interphalangeal (IP) Joints[edit | edit source]
The MTP joints are formed between the metatarsal heads and the corresponding bases of the proximal phalanx. The interphalangeal joints of the toes are formed between the phalanges of the toes. Each toe has proximal and distal IP joints except for the great toe which only has one IP joint.
Joint | Type of Joint | Plane of Movement | Motion |
---|---|---|---|
TC joint | Hinge | Sagittal | Dorsiflexion & Plantarflexion |
ST joint | Condyloid |
Mainly transverse Some sagittal |
Inversion & Eversion Dorsiflexion & Plantarflexion |
MT joint |
TN joint - Ball and socket CC joint - modified saddle |
Largely in transverse Some sagittal |
Inversion & Eversion Flexion & Extension |
TMT joint | Planar | ||
MTP joint | Condyloid |
Sagittal Some Transverse |
Flexion & Extension Abduction & Adduction |
IP joint | Hinge | Sagittal | Flexion & Extension |
Kinematics[edit | edit source]
Cite error: Closing </ref> missing for <ref> tag Motion in other planes is required (like horizontal and frontal plane) to achieve a complete motion for plantarflexion and dorsiflexion.[4] The reported normal available range for dorsiflexion varies in the literature between 0-16.5°[5] and 0-25°[6], and this changes when in weightbearing. The normal range of Plantarflexion has been reported to be around 0°- 50°Subtalar Joint[edit | edit source]The axis of the subtalar joint lies about 42o superiorly to the sagittal plane and about 16 to 23o medial to the transverse plane.[7][8] The literature presents vast ranges of subtalar motion ranging from 5 to 65o.[8] The average ROM for pronation is 5o and 20o for supination. Inversion and eversion ROM has been identified as 30o and 18o, respectively.[9] Total inversion-eversion motion is about 2:1 or 3:2 ratio of inversion-to-eversion movement.[4] Midtarsal Joint[edit | edit source]The midtarsal joint rotates at two axes due to its anatomy, making its motion complex. Longitudinal axis (image 'A' below) lies about 15o superior to the horizontal plane and about 10o medial to longitudinal plane. The oblique axis (image 'B' below) lies about 52o superior to the horizontal plane and 57o from midline. The longitudinal axis is close to the subtalar joint axis and the oblique axis is similar to the talocrural joint axis.
Lisfranc Joint Complex[edit | edit source]The degree of sagittal motion for each TMT joint is presented below:[4]
MTP and IP joints[edit | edit source]The MTP joints are biaxial and move in sagittal and transverse planes. MTP joints have a greater sagittal plane movement and very little transverse plane movement. At the MTP joints, hyperextension is about 90o and flexion is about 30 to 50o. IP joints are hinge joints which limit motion in one direction. Arthrokinematics[edit | edit source]
Influence on Kinetic Chain[edit | edit source]As discussed above with MT joint locking, the transition of foot from pronation to supination is an important function that assists in adapting to uneven terrain and acting as a rigid lever during push off. During pronation, MT joint unlocks providing flexibility of the foot and assists in maintaining balance. And during supination, MT joint locks providing rigidity of the foot and maximizing stability. If the foot stuck pronated, this would lead to hypermobility of the midfoot and place greater demand on the neuromuscular structures that stabilize the foot and maintain upright stance. Whereas if the foot is stuck supinated, the midfoot would be hypomobile, which would compromise the ability of the foot to adjust to the terrain and increase demand on surrounding structures to maintain postural stability and balance. Cote et al[14]concluded that postural stability is affected by foot position im both static and dynamic conditions. Chain reactions occur secondary to positioning of the foot.
In closed chain movement following kinetic chain reaction with over-supinated foot takes place
Arches of Foot[edit | edit source]The arches of foot provide functions of force absorption, base of support and acts as a rigid lever during gait propulsion. The medial longitudinal arch, lateral longitudinal arch and transverse arch are the 3 arches that compromises arches of foot.
Lateral Longitudinal Arch (LLA) – It is the lowest arch and compromises of calcaneus, cuboid and fourth & fifth metatarsal as its bony component. Like MLA the posterior pillar consists of tuberosity of calcaneus whereas the anterior pillar is formed by metatarsal heads of 4th and 5th metatarsals. Plantar aponeurosis, and long & short plantar ligaments provide support for LLA. Peroneus longus tendon plays an important role in maintaining the lateral border of the arch.
Windlass Mechanism of foot – The plantar aponeurosis acts similarly as windlass mechanism. Windlass is typically a horizontal cylinder that rotates with a crank or belt on a chain or rope to pull a heavy objects. The common use of windlass is seen in pulling the anchor of the ship known as anchor windlass. This mechanism can be seen in foot. When the MTP joints are hyperextended, the plantar aponeurosis becomes taut as it is wrapped around the MTP joints. This actions brings the metatarsal and tarsal bones together converting it into a rigid structure and eventually causing the longitudinal arches to rise. This function is important in providing a rigid lever for gait propulsion during push off. Function of the Foot[edit | edit source]The foot requires sufficient mobility and stability for all of its functions. Mobility is necessary for absorbing the ground reaction force of the body.[11] Subtalar pronation has a shock absorbing effect during initial heel contact.[11][1][15][14] Pronation is also necessary to make rotation of the leg possible and to absorb the impact of this rotation. Subtalar pronation plays a role in shock absorption through eccentric control of the supinators.[11] On the other side, the joint of Chopart becomes unlocked so that the forefoot can stay loose and flexible.[1] In midstance, the foot needs mobility to adapt to variation in surfaces.[11][1][15][14] Foot stability is necessary to provide a stable base for the body. The foot needs the capacity to bear body weight and act as a stable lever to propel the body in forward.[11][1][15][14] This function requires pronation control of the subtalar joint.[1][15][14] Normal foot function provides the foot with the capacity to transform at the right time from a mobile adapter to a rigid lever. The foot needs sufficient mobility to move into all the positions of the gait cycle while maintaining mobility and stability.[7][11] Physiological mobility is essential, because if mobility was too large, the foot would not have the capacity to be stable. When this condition is fulfilled, the joint can support standing in the stable maximally close packed position.[11][1] When the normal transition of the two functions isn’t normal many overload injuries can be observed, like in the foot, under leg, upper leg but also in the lower back.[1][15][14] Therefore the three phases of ground contact have to fall in the normal time interval, otherwise some compensation mechanisms (example: genu recurvatum in cases of reduced dorsiflexion) will be used, which cause overuse syndromes.[1][16](Example: chondromalacia, shinsplints...) In the transition from midstance to propulsion phase, the mechanisms often fail. The transition from eversion to inversion is facilitated by the tibialis posterior muscle.[11] The muscle is stretched like a spring and potential energy is stored.[11] At the end of the midstance, the muscle passes from eccentric to concentric work and the energy is released. The tibialis posterior muscle then causes abduction and dorsiflexion of the caput tali in which the hindquarter everted.[11] At the same time, the muscle peroneus longus, at the end of the midstance, will draw the forefoot with a plantar flexion of the first toe.[11] This is how the forefoot becomes stable.[11] When the forefoot moves in the propulsion phase, the windlass phenomena starts. When the dorsiflexion of the metatarsophalangal joints begins the plantar fascia undergoes stress, so the os calcaneus becomes vertical and teared in inversion. Like this, the hindquarter rests in inversion in the unwinding of the forefoot.[11] When there are some abnormalities in the normal gait cycle of functions of the body, some functional ortheses can be used.[1][15][14] This orthese have the capacity to correct the biomechanical function of the foot.[1][15][14] In contrast, insoles only support the arch of the foot. Reduced or limited mobility in the lower limbs can be caused by a articular limitation.[1][15][14] In these cases some classic mobilizations or mobilizations according to manual therapy can be designated.[1][15][14] When the cause is a muscle shortening some stretching can be designated. Also, good (running) shoes are indicated.[17] References[edit | edit source]
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