Foot and Ankle Structure and Function

Anatomy[edit | edit source]

Foot & Ankle

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.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title

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Talocrural (TC) Joint[edit | edit source]

The talocrural joint is formed between the distal tibia-fibula and and 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
Subtalar Joint
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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.

  1. 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.
  2. Chopart's Joint
    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:Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title 

  • 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  Dorsiflesxion & 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

Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title

Kinematics[edit | edit source]

Talocrural Joint[edit | edit source]

The tip of the medial malleoli is anterior and superior to lateral malleoli, which makes its axis oblique to both the sagittal and frontal planes. The axis of rotation is approximately 13-18o laterally from frontal plane and at angle of 8-10o from the transverse plane.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive titleCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title Motion in other planes is required (like horizontal and frontal plane) to achieve a complete motion for plantarflexion and dorsiflexion.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title The normal available range for dorsiflexion is 0-30o and plantarflexion range is 0-55o.

  AnkleAxisPost.jpg           AnkleAxisSup.jpg                                              

Subtalar Joint
STJaxis.jpg
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The axis of the subtalar joint lies about 42o superiorly to the sagittal plane and about 16 to 23o medial to the transverse plane.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive titleCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title The literature presents vast ranges of subtalar motion ranging from 5 to 65o.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title The average ROM for pronation is 5o and 20o for supination. Inversion and eversion ROM has been identified as 30o and 18o, respectively.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title Total inversion-eversion motion is about 2:1 or 3:2 ratio of inversion-to-eversion movement.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title

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.

Midtarsal Longitudinal axis.png

MT Joint LockingCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive titleCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title – An important function of the foot is propulsion of weight during stance phase. This function is made possible by MT joint locking and unlocking. During heel strike, the foot needs to be flexible in order to adjust to the surface and the MT joint unlocks to provide this flexibility. Later in the gait cycle, the foot then needs to act as a rigid lever to propel the weight of the body forward which is made possible by MT joint locking. During pronation/eversion of the foot, the axis of the TN and CC joints are parallel to each other, making it easier for them to independently move and unlock the MT joint. The axes cross each other during supination/inversion which locks the MT joint making it difficult to move. Blackwood et al concluded in the study that there is increased forefoot movement when calcaneus is everted. This is consisted with the MT joint locking mechanism.

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Lisfranc Joint Complex[edit | edit source]

The degree of sagittal motion for each TMT joint is presented below:Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title

TMT Joint Degree of Motion
1st 1.6o
2nd 0.6o
3rd 3.5o
4th 9.6o
5th 10.2o


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]

  1. Talocrural Joint – Talus rolls within the mortise during dorsiflexion and plantarflexion. During dorsiflexion, the talus rolls anteriorly and it glides posteriorly. While with plantarflexion, talus rolls posteriorly and glides anteriorly.
  2. Subtalar Joint – Secondary to the anatomy of the subtalar joint, the coupled motion of dorsiflexion, abduction and eversion produces pronation, whereas the coupled motion of plantarflexion, adduction and inversion produces supination. It presents two point of articulations – anterior talocalcaneal articulation and posterior talocalcaneal articulation.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title During open kinectic chain inversion, the calcaneus rolls into inversion and it glides/slides laterally. And during eversion, the calcaneus rolls into eversion and it glides/slides medially
  3. Midtarsal Joint – For Talonavicular joint, the concave navicular moves on convex talus and hence the roll and glide is in the same direction of movement. The calcaneocuboid joint is a saddle joint so the direction changes depending on the movement. During flexion-extension, the cuboid is concave and the calcaneus is convex; hence, the roll and glide occurs in the same direction as the talonavicular joint. During abduction-adduction, however, the cuboid is convex and calcaneus is concave, and therefore the roll and glide occurs in the opposite direction.
  4. Lisfranc Joint – Secondary to bony and ligamentous anatomy of the complex, its primary role is stability of the midfoot and has very little movement. It has three distinct arches and the main stabilizing structure of TMT joint is a Y-shaped ligament known as Lisfranc’s ligament. 
  5. MTP and IP Joints – Glide and roll is in the same direction as the movement for the MTP joints as the concave base of the phalanx moves on the convex head of the metatarsal. The same is true for the IP joints, where glide and roll is in the same direction as the concave distal phalanx moves on the convex proximal phalanx.


Joint Closed-Packed Position Open-Packed Position Capsular Pattern Concave Surface Convex Surface

Concave-convex rule

Roll & glide

Talocrural joint Full dorsiflexion 10o of plantarflexion and midway between pronation and supination Limitation of plantarflexion, although clinically dorsiflexion limitation is more common Proximal - Mortise formed by Tibia, tibiofibular ligament and fibula Distal - Trochlear surface of Talar dome Opposite direction
Subtalar joint Full inversion Inversion/plantarflexion Limitation of inversion in chronic arthritis. Limitation of eversion in traumatic Proximal - Anterior, middle and posterior facet of talus Distal – Calcaneal Anterior, middle and posterior talar articular surface Opposite direction
Talonavicular joint Full supination Midway between extreme ROM Limitation of dorsiflexion, plantarflexion, adduction and internal rotation. Proximal - Head of Talus Distal - Concavity on Navicular bone for talus Same direction
Calcaneocuboid joint Full supination Midway between extreme ROM Limitation of dorsiflexion, plantarflexion, adduction and internal rotation. Distal - Cuboid is concave during flexion-extension.
Calcaneus is concave during adduction-abduction
Proximal - Calcaneus is convex during flexion-extension.
Cuboid is convex during adduction-abduction

Flexion-extension = Same direction
Adduction-abduction = Opposite direction

Lisfranc joint Full supination Midway between supination and pronation
1st MTP joint Hyperextension Slight (10o) extension Loss of motion more in extension than flexion Distal - Base of phalanx Proxmial - Head of Metatarsal Same direction
2nd to 5th MTP joint Maximum flexion Slight (10o) extension Loss of flexion Distal - Base of phalanges Proximal - Head of metatarsals Same direction
Interphalangeal Joint Full extension Slight flexion Restriction in all direction with more in extension Distal Phalanx Proximal Phalanx Same direction

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 placing greater demand on the neuromuscular structure stabilize foot and maintaining upright stance. Whereas if the foot is stuck supinated, the midfoot would be hypomobile which would compensate the ability of the foot to adjust to the terrain and increasing demand on surrounding structure to maintain postural stability and balance. Cote et alCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive titleconcluded that postural stability is affected by foot positioning under static and dynamic conditions. Chain reaction occurs secondary to positioning of the foot.

In closed chain movement following kinetic chain reaction with overpronated foot takes place

Kinetic chain.png
  • Calcaneal eversion
  • Adduction and plantarflexion of talus
  • Medial rotation of talus
  • Medial rotation of tibia and fibula
  • Valgus at knee
  • Medial rotation of femur
  • Anterior tilting of pelvis

In closed chain movement following kinetic chain reaction with oversupinated foot takes place

  • Calcaneal inversion
  • Abduction and dorsiflexion of talus
  • Lateral rotation of talus
  • Lateral rotation of tibia and fibula
  • Varus at knee
  • Lateral rotation of femur
  • Posterior tilting of pelvis

Arches of Foot
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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.


Medial Longitudinal Arch (MLA) – It is the longest and highest of all the arches. Bony components of MLA include calcaneus, talus, navicular, the three cuneiform bones and first 3 metatarsal. The arch consists of two pillar: anterior and posterior pillars. Anterior pillar consists of head of first 3 metatarsal heads whereas posterior pillar consists of tuberosity of calcaneus. Plantar aponeurosis forms the supporting beam connecting the two pillarsCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title. Apex of the MLA is superior articular surface of talus. In addition to plantar aponeurosis the MLA is also supported by spring ligament and deltoid ligament. Tibialis anterior and posterior muscles play an important role in raising the medial border of the arch, whereas flexor hallucis longus acts as bowstring.  


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.

Arches of foot.jpg
Transverse Arch – It is concave in non-weight bearing which runs medial to lateral in midtarsal and tarsometatarsal area. The bony component of the arch consists of metatarsal heads, cuboids and 3 cuneiform bones. The medial and lateral pillars of the arch is formed by medial and lateral longitudinal arch respectively. The arch is maintained by posterior tibialis tendon and peroneus longus tendon which cross the plantar surface from medial to lateral and lateral to medial respectively.


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.

Windlass.jpg

Biomechanical evaluation[edit | edit source]

Tibial Torsion Measurement/Thigh-foot angle (TFA) – To measure internal or external tibial torsion, patient is positioned in prone lying with knees flexed to 90o. A thigh-foot ankle (TFA) is measured between the line bisecting the posterior thigh and another line bisecting the foot. Normally the angle is between 0o to 30o, TFA more than 30o is excessive external tibial torsion and TFA less than 0o is considered internal tibial torsion[4].

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TC joint ROM – TC joint ROM of dorsiflexion and plantarflexion is taken with knee flexed, if the knee is extended the tightness of gastrocnemius can overshadow the TC joint ROM. Fulcrum of the goniometer is placed approximately 1.5 cm inferior to lateral malleoli. Stationary arm is parallel to longitudinal axis of fibula with taking head of fibula as the reference point. And the moveable arm is parallel to the longitudinal axis of 5th metatarsal with head of 5th metatarsal as referenceCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.

Subtalar Joint Neutral (STJN)Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title,Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title – It is the position in which the foot is neither pronated nor supinated. STJN acts as a reference point for STJ PROM and for lower extremity measurements. It is also the position which is used for orthosis fabrication and casting. To find STJN in OKC patient is in prone lying with the foot to be measured off the plinth and other lower extremity in the position to make a “4”. The talus is palpated between the thumb and index finger, and the forefoot is moved gently into supination-pronation to the point where medial and lateral aspect of talus are palpated equally on both sides. The foot is then moved into slight dorsiflexion until a soft end-feel, this is STJN position.

Calcaneal angle measurement (tibia to calcaneus angle) – For OKC measurement, once the STJN is established the angle between the line bisecting calf and another line bisecting calcaneus is taken. Normally the calcaneal angle is in 2o to 8o of varus/inversion. For CKC measurement, patient is standing on a box in unilateral stance position with support for balance. The talar dome congruency is palpated and the joint is place in STJN. The angle between the line bisecting the calf and the line bisecting the calcaneal is taken in this position.

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STJ ROM – PROM for subtalar joint is measured in OKC. Patient placement and goniometric placement is same as measurement of calcaneal angle. From STJN, the calcaneus is passively inverted and everted and maximum range is measured. The total subtalar inversion/eversion is measured from calcaneal angle. For example, if calcaneal angle is 5o (of calcaneal inversion) and STJ total passive inversion is 20o, then the STJ inversion is 15o (20o-5o). And if STJ total passive eversion is 10o, then STJ eversion is 15o (10o+5o).

MTP and IP ROM – For measurement of 1st MTP fulcrum of goniometer is placed on the medial aspect of 1st MTP joint axis. Stationary arm is parallel to the floor and movable arm is parallel to the proximal phalanx of great toe[7]. Normal ROM for flexion is 0-45o, and for extension is 0-70o. Normal ROM for lateral four MTP flexion is 0-40o, and lateral four MTP extension is 0-40o. Normal ROM for great toe IP flexion is 0-90o, and great toe IP extension is 0o. Normal ROM for lateral four PIP flexion is 0-35o and PIP extension is 0o. And normal ROM for lateral four DIP flexion is 0-60o and extension is 0-30oCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.

Forefoot angle – The relationship of forefoot to rearfoot is measured to quantify forefoot varus or forefoot valgus. To measure the relationship, patient is prone lying with figure ‘4’ position for non-examined lower extremity. Once the STJN is achieved the relationship of forefoot to rearfoot is observed. The stationary arm of the goniometer is place perpendicular to line bisecting calcaneus with fulcrum on the point bisecting calcaneus. The movable arm of the goniometer is placed parallel to imaginary line passing through metatarsal heads. Forefoot angle of 0o is considered neutral, whereas positive degree is forefoot varus and negative degree is forefoot valgusCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.

[8] Longitudinal Arch Angle (LAA)

Longitudinal Arch Angle

A line is drawn from center of medial malleoli to navicular tuberosity and another line is drawn from navicular tuberosity to head of first metatarsal. The obtuse angle between these lines is known as LAA. The normal maximum LAA is between 1310 and 1520. Foot with lower LAA is considered to have low-arch and angle greater than 1520 is considered to be high-archedCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title,Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title. Feiss line is drawn from center of medial malleoli to head of 1st metatarsal. If it is high arch the navicular tuberosity is above the arch and in low-arched foot the navicular tuberosity is below the lineCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.

Foot Posture Index (FPI) – It is a clinical tool used to quantify the degree to which a foot is pronated, neutral or supinated. A series of six observations and palpation are made by clinician and each measure is scored from -2 to 2. A total score of 0 is considered a neutral foot, a positive score is for pronated foot whereas supinated foot is given negative score. For scoring patient stands in double stance position and is asked to stand still. Following table describes the scoring criteria of FPI taken from Lee et alCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.

-2 -1 0 +1 +2
Talar head palpation Talar head palpable on lateral side/but not on medial side Talar head palpable on lateral/slightly palpable on medial side Talar head equally palpable on lateral and medial side Talar head slightly palpable on lateral side/palpable on medial side Talar head not palpable on lateral side/but palpable on medial side

Supra and infra lateral malleoli curvature (viewed from behind)

Curve below the malleolus either straight or convex Curve below the malleolus concave, but flatter/more than the curve above the malleolus Both infra and supra malleolar curves roughly equal Curve below the malleolus more concave than curve above malleolus Curve below the malleolus markedly more concave than curve above malleolus
Calcaneal frontal plane position (viewed from behind) More than an estimated 5o inverted (varus) Between vertical and an estimated 5o inverted (varus) Vertical Between vertical and an estimated 5o everted (valgus) More than an estimated 5o everted (valgus)
Prominence in region of TNJ (viewed at an angle from inside Area of TNJ markedly concave Area of TNJ slightly, but definitely concave Area of TNJ flat Area of TNJ bulging slightly Area of TNJ bulging markedly
Congruence of medial longitudinal arch (viewed from inside) Arch high and acutely angled towards the posterior end of the medial arch Arch moderately high and slightly acute posteriorly Arch height normal and concentrically curved Arch lowered with some flattening in the central position Arch very low with severe flattening in the central portion - arch making ground contact
Abduction/adduction of forefoot on rearfoot (view from behind) No lateral toes visible. Medial toes clearly visible Medial toes clearly more visible than lateral Medial and lateral toes equally visible Lateral toes clearly more visible than medial No medial toes visible. Lateral toes clearly visible.

Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title

Arch Height Index (AHI) – AHI is used to measure medial longitudinal arch and based on which foot can be categorized into high-arched, normal and low-arched. Williams & McClayCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title compared various foot measurements and ratios, and came up to the conclusion that height of dorsum of foot at 50% of foot length divided by truncated foot length was reliable and valid measure to determine AHI. A caliper and a graph-sheet can be used for the measurement. Patient is in standing position and caliper is used to measure foot length, height of the dorsum of the foot at 50% of foot length and truncated foot length as shown in the image.

Arch Index

AHI = Height of the dorsum of foot at 50% of foot length

                      Truncated foot length


If the ratio is 0.356 or greater the foot is considered high arched, and ratio of less than or equal to 0.275 is considered a low-arched foot. Description of arch mobility can be assessed by having AHI taken at 10% and 90% of body weight. Arch Rigidity Index (ARI) is also been suggested which is calculated as standing AHI/sitting ARI and it can offer a valid and reliable alternative to navicular drop testCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.

Navicular Drop Test


References[edit | edit source]

  1. Anatomy Zone. Ankle Joint - 3D Anatomy Tutorial. Available from: https://www.youtube.com/watch?v=lPLdoFQlZXQ [last accessed 19/03/2015]
  2. AnimatedBiomedical. Ankle Joint, Bones of the Foot - 3D Medical Animation. Available from: https://www.youtube.com/watch?v=X-eAXKS4pJM [last accessed 19/03/2015]
  3. Midtarsal joint axis during pronation. Available from: https://vimeo.com/65147465
  4. Stuberg W, Temme J, Kaplan P, Clarke A, Fuchs R. Measurement of tibial torsion and thigh-foot angle using goniometry and computed tomography. Clinical orthopaedics and related research. 1991 Nov 1;272:208-12.
  5. PT thigh foot angle. Available from: https://www.youtube.com/watch?v=SnOXxzyMAOs
  6. Assessing subtalar neutral. Available from https://www.youtube.com/watch?v=zdGgCxVyBRo
  7. Creighton DS, Olson VL. Evaluation of range of motion of the first metatarsophalangeal joint in runners with plantar faciitis*. Journal of Orthopaedic &amp;amp;amp;amp;amp;amp; Sports Physical Therapy. 1987 Jan;8(7):357-61.
  8. Prone Exam: Forefoot To Rearfoot Alignment. Available from https://www.youtube.com/watch?v=Mvm8krHIOAI