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ANKLE AND FOOT ANATOMY

Bone and Joint Anatomy
Ligaments
Muscles
Kinesiology


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BONE and JOINT ANATOMY

   	  The center of this ring is the bone called the talus. The 
    talus bone has a shiny joint surface covering which allows your 
    ankle to glide effortlessly across the shiny undersurface of your
    large leg bone called the tibia. When these two bones meet they 
    form your ankle joint. On the outside of your ankle you will find 
    a smaller, thin bone called the fibula. This bone helps prevent your 
    major ankle bone from shifting outward. On the other side of your 
    ankle you will find a bump on the inside which is connected to the 
    larger leg bone called the tibia. This part of the tibia is called the 
    malleolus which just means, "hammer" in Latin. The stability of your 
    ankle joint is dependent upon the ability of these bones to keep 
    the central bone in place while the ankle moves back and forth. The 
    joint is more stable when your foot is flat on the floor. The ankle is 
    more rigidly held in place by the bony stabilizers of the fibula and 
    malleolus because they are closer to the talus. However, when you
    point your toes, your ankle becomes unstable because the distance
    between the bony stabilizers of your ankle becomes larger. Thus, your 
    ankle than relies more and more on the soft tissues including your 
    ligaments to continue to provide stability. Since soft tissues are 
    "softer" than your bones, you become more vulnerable to a sprain 
    when you are pointing your toes.

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LIGAMENTS

  A. Medial Ligaments 
  	  - The deltoid ligament stabilizes the ankle medially. Superficial
       and deep layers of the deltoid ligament may independently prevent 
       valgus talar tilting. 
  
  B. Lateral Ligaments 
	  - The anterior talofibular ligament (ATFL), calcaneofibular 
        ligament (CFL), and posterior talofibular ligament (PTFL) all 
        contribute to alleviate anterior drawer stress in the nonaxially 
        loaded ankle, as well as adduction (varus talar tilting) stresses 
        in the plantarflexed, neutral, and dorsiflexed ankle/subtalar 
        complex.  

  C. Ligaments of the Subtalar Joint 
	  - The CFL is a primary stabilizer of the subtalar joint that 
       traverses the lateral side of the posterior facet articulation. The 
       cervical ligament is the strongest ligament connecting the talus 
       and calcaneus, and extends from the inferior aspect of the talar 
       neck, across the sinus tarsi, to the dorsum of the neck of the 
       calcaneus. 

  D. Hindfoot and Midfoot Ligaments
	  - The V-shaped bifurcate ligament (ligament of Chopart), 
       consisting of: the lateral calcaneonavicular and medial calcaneo-
       cuboid ligaments, extends from the dorsal neck of the calcaneus 
       across the dorsal calcaneonaviculocuboid region, stabilizing the 
       calcaneus to the navicular and cuboid bones.  
    	  - The long (superficial) and short (deep) plantar ligaments 
       extend from the plantar surface of the calcaneus to the plantar 
       aspect of the cuboid. 
  	  - The long plantar ligament divides into four slips, which 
       insert on the plantar aspect of the second to fifth metatarsal 
       bases. 
	  - The tarsometatarsal joints are stabilized by multiple 
       dorsal, plantar, and interosseous tarsometatarsal ligaments, 
       including Lisfranc's (interosseous first cuneiform-second 
       metatarsal) ligament.  

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MUSCLES

  INTRINSIC MUSCLES

  Abductor Digiti Minimi
   O: Calcaneus tuberosity	                            	
   I: Base of 5th proximal phalanx	
   A: Digits: Abduction of little toe	
   I: Medial and Lateral Plantar Nerve

  Abductor Hallucis
  O: Calcaneous	
  I: Base of 1st toe	
  A: Digits: Abduction of big toe	
  I: Medial and Lateral Plantar Nerve

  Flexor Digitorum Brevis
  O: Calcaneus tuberosity	
  I: The base of 4 lesser toes	
  A:Digits: Flexion of lesser toes	
  I: Medial and Lateral Plantar Nerve

  Lumbricals
  O: Flexor Digitorum Longus tendon	
  I: Base of the proximal phalanges of lesser toes	
  I: Medial and Lateral Plantar Nerve

  Quadratus Plantae
   O: Calcaneus tuberosity	
   I: Flexor Digitorum Longus tendon	
   A: None | Digits: Flexion	
   I: Medial and Lateral Plantar Nerve

  Adductor Hallucis
   O: Transverse Head: Head of metatarsals; Oblique Head	
   I: Base of the 1st and 2nd proximal phalanges	
   A: Digits: Adduction of big toe	
   I: Medial and Lateral Plantar Nerve

  Flexor Digiti Minimi Brevis
   O: Bifurcated origin off mid-tarsal bone	
   I: Base of 5th meta tarsal	
   A: Digits: Flexion of big toe	
   I: Medial and Lateral Plantar Nerve

  EXTRINSIC MUSCLES

  Extensor Digitorum Longus
   O: Tibia, fibula, and interosseus membrane	
   I: Four distal phalanges	
   A:DIGITS: EXTENSION | Ankle: Dorsiflexion	
   I: Deep Peroneal Nerve

  Extensor Hallucis Longus
   O: Tibia, fibula, and interosseus membrane
   I: Base of the first tibial phalanx	
   A: DIGITS: DORSIFLEXION OF BIG TOE		
   I: Deep Peroneal N.

  Tibialis Ant.
   O: Proximal tibia	
   I: Base of the 1st metatarsal and cuneiform	
   A: Foot: Inversion; Ankle: Dorsiflexion		
   I: Deep Peroneal Nerve

  Extensor Digitorum Brevis
   O: Proximal tibia
   I: Base of the 1st metatarsal and cuneiform	
   A: Foot: Inversion; Ankle: Dorsiflexion
   I: Deep Peroneal Nerve

  Extensor Hallucis Brevis
   O: Proximal tibia
   I: Base of the 1st metatarsal and cuneiform	
   A: Digits: Extension of big toe
   I: Deep Peroneal Nerve

  Peroneus Brevis
   O: Distal fibula	
   I: Base of the 5th metatarsal	
   A: Foot: Eversion		
   I: Superficial Peroneal Nerve

  Peroneus Longus
   O: Distal fibula
   I: Base of 1st and 2nd metatarsals	
   A: Foot: Eversion | Foot: Plantarflexion		
   I: Superficial Peroneal Nerve

  Flexor Digitorum Longus
   O: Distal fibula
   I: Base of the distal phalanges of the lesser toes	
   A: Digits: Plantarflexion		
   I: Tibial Nerve

  Flexor Hallucis Longus
   O: Distal fibula
   I:Base of the 1st distal phalanx 
   A: Digits: Plantarflexion of big toe		
   I: Tibial Nerve

  Popliteus
   O: Tibia	
   I: Between the lateral meniscus and 
       lateral collateral ligament of the knee	
   A: None | Stabilize the knee		
   I: Tibial Nerve

  Tibialis Posterior
   O: Posterior Tibia	
   I: Navicular and Cuneiform	
   A: Foot: Inversion		
   I: Tibial Nerve

  Gastrocnemius
   O: Lateral and medial condyles of the femur	
   I: Achilles Tendon	
   A: Foot: Plantarflexion		
   I: Tibial Nerve

  Plantaris
   O: Lateral side of femo ral condyle	
   I: Achilles Tendon	
   A: Knee: Flexion; Ankle: Plantarflexion		
   I: Tibial Nerve

  Soleus
   O: On the tibia, below the knee	
   I: Achilles Tendon	
   A: Ankle: Plantarflexion		
   I: Tibial Nerve


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KINESIOLOGY


  Stability of the ankle joint depends on:  
	  1. Ankle position -determines the orientation of ligaments 
	  2. Applied load (weightbearing) - instability occurs during 
                                          loading or unloading.  
	  3. Ligament complexes 
  
 Rotatory stability of the ankle joint is determined by: 
   	  1. the collateral and syndesmosis ligaments 
	  2. fit of the talus in the mortise 
	  3. shape of the articular surfaces in the loaded condition  
	  4. the ATFL, CFL and PTFL in the loaded ankle  
	  5. the deltoid and syndesmosis ligaments

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