Structure and Function of the Foot and Ankle

 

 

  Ankle:   

 

• Also known as the talocrural articulation, the ankle joint is a hinge synovial joint.  

• During movement of the joint the tibia and fibula grip the the trochlea of the talus in what is called the malleolar mortise. 
• includes the distal part of the leg, with the joint between the medial and lateral malleoli and the superior part of the talus.

   

• Bones of the Ankle:
  • tibia (long bone)-second largest bone in body; the weight-bearing bone of the lower leg; ankle portion consists of the vertical tibial shaft, the medial expansion extending inferior to the rest of the shaft named the medial malleolus, and a groove that accommodates the distal end of the fibula named the fibular notch.
  • fibula (long bone)- has no function in weight bearing; ankle portion enlarges after the shaft to prolong laterally and inferiorly as the lateral malleolus,
  • talus (also considered a bone of the foot; listed below)

 

 

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 Foot and Toes:

 

• Provides a platform for supporting the body when standing and has important role in locomition.
• The part of the foot contacting the floor is the plantar surface, and the part directed superiorly is the dorsal surface of foot.

• Anatomical zones of the foot

  • Rearfoot- formed by the calcaneous and talus, provides stability and shock absorption during the initial stance phase during gait. Also serves as a lever arm during plantarflexion of the foot and ankle
  • Midfoot- formed by the navicular, three cuneiforms, and cuboid bones, serves as the shock-absorbing segment of the foot.
  • Forefoot + Toes- formed by the 5 metatarsals, and 14 phalanges, serves as a lever during the preswing phase of gait.
• 7 tarsals: (short bones)

  •  calcaneus- largest and strongest bone of foot. Most prominent feature is the calcaneal tubercle which projects posteriorly as a lever for plantar flexion, it is the weight bearing prominence on the calcaneus.            

  • The calcaneal body is the origin and insertion for many of the ligaments and muscles acting on the foot and ankle.
  • The sustentaculum tali arises off the anterior superior medail surface of the calcaneal body to help support the talus.
  • The peroneal tubercle, projecting off the lateral side of the calcaneous, helps maintain stability of the peroneal tendons.  
  • talus- sits under distal tibia and fibula. It is a saddle-shaped bone that has a body, neck, and head. With no muscular/tendinous attachments, the talus acts as an interface between the foot and ankle.
    • (articulates superiorly w/ distal end of tibia, medially w/ medial malleolus, laterally w/ lateral malleolus, inferiorly w/ calcaneous, anteriorly w/ navicular)
    • Its inferior surface contains anterior, middle, and posterior facets which provide a base for weight bearing and provide w/ a site for ligaments to attach.
    • The superior surface contains facets for articulation with the tibia.
  • navicular- "keystone" of the medial longitudinal arch (articulates anteriorly w/ 3 cuneiforms, cuboid laterally, and talus posteriorly). 
    • The navicular tuberosity arises from the medial aspect of the navicular as the primary insertion for the tibialis posterior muscle. 

  • cuboid-(cubical in shape)  sulcus of cuboid is formed anterior to the cuboid tuberosity and posterior to the base of the 5th metatarsal.
    • (articulates with 3rd cuneiform and navicular medially, 4th and 5th metatarsals anteriorly, and the calcaneous posteriorly)
  • Cuneiforms- Three cuneiform bones are identified by their relative positions on the foot. 
    • Medial (first) largest cuneiform (articulates with navicular posteriorly, 1st metatarsal anteriorly, and intermediate cuneiform laterally). 
    • Intermediate (second) smallest cuneiform (articulates with navicular posteriorly, 2nd metatarsal anteriorly, and medial and lateral cuneiform). 
    • Lateral (third), (articulates with navicular posteriorly, 3rd metatarsal anteriorly, intermediate cuneiform medially, and medial aspect of the cuboid laterally).     

        

• 5 metatarsals: (long bones) each having a proximal base, body, and distal head. Named numerically from medial as first to lateral as fifth. (The bases the metatarsals articulate with the neighboring metatarsal with a tight fit and the bases of the first three metatarsals articulate proximally with the corresponding cuneiform, and the 2nd metatarsal also articulates with the first cuneiform. The 4th and 5th metatarsals articulate with the cuboid. Each metatarsal head also articulates with the proximal phalanx of the corresponding toe, and loosely with the neighboring metatarsal heads.
• 14 phalanges: (long bones) each toe consists of three phalanges (distal, middle, and proximal) aside from the great toe which only has proximal and distal. Named numerically, from one through five from medial to lateral. Each phalanx has a base, shaft, and head (on a very small scale). In elderly people, the middle and distal phalanges of the 5th digit may be fused.

 

 

 

 

 

                                                                             

 

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Joints:                                                                                                          

 

•     

  Joints	Type	Articulating Surfaces	Movements
  Ankle (Talocrural)	Hinge synovial	Talus articulates with the distal ends of tibia and fibula	Dorsi flexion, plantar flexion
  Subtalar	plane synovial joint	Posterior calcaneal surface of talus articulates with posterior articular facet of calcaneus.	Inversion/Eversion
  Talocalcaneonavicular	Part Ball and Socket synovial Joint	Head of talus articulates with posterior portion of navicular and anterior border of calcaneus.	Rotation
  Calcaneocuboid	Plane synovial	Posterior aspect of cuboid articulates with anterior border of calcaneus	Inversion/Eversion of foot and circumduction
  Cuneonavicular	Plane synovial	Bases of metatarsal bones articulate with anterior portion of navicular	Limited movement
  Tarsometatarsal	Plane synovial	Bones of the mid-foot articulate with bases of metatarsal bones	Gliding, sliding
  Intermetatarsal	Plane synovial	Bases of metatarsal bones articulate with adjacent bases	Some gliding, sliding occurs
  Metatarsophalangeal	Condyloid synovial	Bases of phalanges articulate with heads of metatarsal bones	Flexion/Extension, limited Abduction/Adduction, and circumduction
  Interphalangeal	Hinge synovial	Base of one phalanx articulates with head of one proximal to it	Flexion/Extension of toes

 

               

DEFINITION OF JOINTS
Synovial:	he two surfaces which articulate contain hyaline cartilage on their ends. They contain joint capsules which hold synovial fluid to noursih the cartilage.
Hinge:	Motion in one plane. Flexion and extension.
Condyloid:	Motion in multiple planes. Able to do flexion/extension, abduction/adduction, and circumduction, but no rotation.
Plane:	Motion is slight, and in only one plane. More of a gliding motion.
Ball and Socket:	Distal bone is capable of motion around multiple axes. It is able to do flexion/extension, abduction/adduction, circumduction, and rotation.

 

 

Ligaments:

 

 

 

 

Major Ligaments of Foot and Ankle: 

 

• Anterior Talofibular Lig
  • Resists inversion of talocalcaneal unit in plantar position and limits anterior translation of the talus on the tibia
• Posterior Talofibular Lig
  • Limits posterior displacement of talus on tibia
• Anterior Tibiofibular Lig
  • Resists separation of tibia and fibula
• Posterior Tibiofibular Lig
  • Resists separation of tibia and fibula

 

http://www.aafp.org/afp/20061115/1714-f1.jpg

 

• Long Plantar Lig
  • Maintains longitudenal arch of foot
• Calcaneocuboid Lig (short plantar lig)

   

  • Maintains longitudenal arch of foot
• Calcaneonavicular Lig (Spring Ligament)
  • Supports head of talus and transfers weight from talus to maintain longitudenal arch of foot
• Calcaneofibular Lig
  • Resists talar inversion within mid-range of talocrural motion
• Tibionavicular Lig
  • Limits lateral translation and lateral rotation of the tibia on the foot
• Deltoid Lig
  • Provides medial support of ankle, prevents excessive eversion of talus
  • Composed of anterior tibiotalar, tibiocalcaneal, and posterior tibiotalar lig.

Minor Ligaments of Foot and Ankle: 

 

• Dorsal calcaneocubiod Lig
• Dorsal metatarsal Lig
• Dorsal Tarsometatarsal Lig
• Dorsal intercuneiform Lig
• Dorsal cuneonavicular Lig
• Dorsal cuboideonavicular Lig
• Dorsal talonavicular Lig
• Lateral Talocalcaneal Lig

 

Range of Motion of Ankle and Foot:

• Ankle
  • dorsiflexion (lifting foot)
  • plantar flexion (pointing foot). When the foot is plantar flexed, it is possible to have small amounts of abduction, adduction, inversion, and eversion.
• Foot and Toes
  • inversion (supination) of the metatarsophalangeal joints
  • eversion (pronation) of the metatarsophalangeal joints
  • extension of the metatarsophalangeal and interphalangeal joints
  • flexion of the metatarsophalangeal and interphalangeal joints

  •  

    When running, the foot is slightly inverted at contact, following contact it everts to a maximum pronated position at mid-stance before inverting through to toe-off.

 

 Weight-bearing areas of the foot:

 

 

 

• Weight is transferred from the knee joint to the tibia 
• The load is applied from the inferior surface of the tibia to the medial surface of the talus
• The talus distributes the load as the tup of the arch formed by the tarsal and metatarsal bones and evenly distributed to be supported at the heel and metatarsophalangeal joints.

 

 

 

***Information from this web page has been derived from the following sources:

•    Keith Moore and Arthur Dalley. Clinically Oriented Anatomy 5th ed. Copyright 2006 Lippincott Williams and Wilkins.
• McGinnis, Peter M. Biomechanics of Sports and Exercise. Copyright 1999 Peter M. McGinnis.
• Chad Starkley and Jeff Ryan. Evaluation: of Orthopedic and Athletic Injuries 2nd Ed. Copyright 2002 FA Davis Co.

 

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