Ankle and Foot 1

• ANKLE & FOOT COMPLEX

  •is structurally analogous to the wrist/hand complex

  •is able to sustain large weight-bearing stresses while accommodating to a variety of surfaces and activities

  •must be stable to provide an adequate base of support and function as a rigid lever for pushing-off when walking, running, or jumping

  •must also be mobile to adapt to uneven terrain, absorb shock as the foot hits the ground, and dampen rotations imposed by the more proximal joints of the lower extremity
• has 28 bones that form 25 component joints

  • proximal and distal tibiofibular joints
  • talocrural (ankle) joint
  • talocalcaneal (subtalar) joint
  • talonavicular and calcaneocuboid joints (transverse tarsal joints)
  • Five tarsometatarsal joints
  • metatarsophalangeal joints
  • nine interphalangeal joints
• bones of the foot are traditionally divided into three functional segments:

  • the hindfoot (posterior segment) - composed of the talus and calcaneus
  • the midfoot (middle segment) - composed of the navicular, cuboid, and three cuneiform bones
  • the forefoot (anterior segment) - composed of the metatarsals and the phalanges
• three motions of the ankle/foot complex that approximate cardinal planes and axes:

  • dorsiflexion / plantarflexion
  • inversion /eversion
  • abduction /adduction
• Dorsiflexion


  Motion that decreases the angle between the leg and the dorsum of the foot
• Abduction and adduction occur approximately in the transverse plane around a vertical axis

  • Abduction occurs when the distal aspect of a segment moves away from the midline of the body (or away from the midline of the foot in the case of the toes); adduction is the opposite
• Plantarflexion


  Motion that increases the angle between the leg and the dorsum of the foot
• Pronation and supination in the foot are motions that occur around an axis that lies at an angle to each of the axes for “cardinal” motions of dorsiflexion/plantarflexion, inversion/ eversion, and abduction/adduction

  
  

  In non-weightbearing:

  
  

  • pronation is a coupled motions of dorsiflexion, eversion, and abduction
  • supination is a coupled motions of plantarflexion, inversion, and adduction
• Extension (of toes)


  Bringing the toes up
• ANKLE JOINT

  •refers specifically to the talocrural joint

  •the articulation between the distal tibia and fibula proximally and the body of the talus distally

  •has a single oblique axis with one degree of freedom with the motions of dorsiflexion/plantarflexion
• Flexion (of toes)


  Bringing the toes down or curling them
• PROXIMAL ARTICULAR SURFACES

  • concave surface of the distal tibia and of the tibial and fibular malleoli
  • is referred to as  “ mortise ” (wrench-like)
  • these three facets form an almost continuous concave joint surface 

  ➢ extends more distally on the fibular (lateral) side than on the tibial (medial) side 

  
  

  ➢ extends more distally on the posterior margin of the tibia than on the anterior margin

  
  

  • is adjustable , relying on the proximal and distal tibiofibular joints to both permit and control the changes in the mortise
• Inversion


  Motion that brings the plantar surface of the segment toward the midline
• PROXIMAL TIBIOFIBULAR JOINT

  • a plane synovial joint formed by the articulation of the head of the fibula with the posterolateral aspect of the tibia
  • a convex tibial facet and concave fibular facet
  • surrounded by a joint capsule that is reinforced by anterior and posterior tibiofibular ligaments
• Eversion


  Motion that is the opposite of inversion
• Dorsiflexion and plantarflexion are motions that occur approximately in the sagittal plane around a coronal axis
• DISTAL TIBIOFIBULAR JOINT

  
  

  • syndesmosis, or fibrous union, between the concave facet of the tibia and the convex facet of the fibula

  ➢ do not actually come into contact with each other but are separated by fibroadipose tissue

  • although there is no joint capsule, all ligaments between the tibia and fibula contribute to stability at both the proximal and distal tibiofibular joints
  • the anterior and posterior tibiofibular ligaments and interosseous membrane provide support to the distal tibiofibular joint

  ➢ interosseous membrane directly supports both proximal and distal tibiofibular articulations
• Inversion and eversion occur approximately in the frontal plane around a longitudinal axis
• • talocrural joint is dependent on stability of the tibiofibular mortise

  ➢ ankle mortise would be unable to grasp and hold on to the talus if the tibia and fibula were permitted to separate or if one side of the mortise were missing

  • ankle mortise must have some mobility function

  ➢ mobility role of the mortise belongs primarily to the fibula

  • the proximal tibiofibular joint must be mobile

  ➢ if the proximal tibiofibular joint is mobile, so too must the distal tibiofibular joint be, because the two joints are mechanically linked
• DISTAL ARTICULAR SURFACES

  • body of the talus 
  • wider anteriorly than posteriorly (wedge-shaped)
  • has three articular surfaces

  =>large lateral (fibular) facet

  =>smaller medial (tibial) facet

  =>trochlear (superior) facet - has a central groove that runs at a slight angle to the head and neck of the talus
• CAPSULE AND LIGAMENTS

  • capsule is fairly thin and especially weak anteriorly and posteriorly therefore stability depends on the intact ligament structures
  • also reinforced by portions of the extensor and peroneal retinaculum
  • ligaments that support the proximal and distal tibiofibular joints:

  => crural tibiofibular interosseous ligament

  => anterior tibiofibular ligaments

  => posterior tibiofibular ligaments

  => tibiofibular interosseous membrane
• major ligament complexes that maintain congruence of the mortise and talus and control medial-lateral joint stability:

  
  

  • medial collateral ligament (MCL) 
  • lateral collateral ligament (LCL) 

  => also provide support for the subtalar (or talocalcaneal) joint that they also cross
• medial collateral ligament 

  • is most commonly called the “deltoid ligament”
  • fan-shaped and extremely strong
  • arise from the tibial malleolus and insert on the navicular bone anteriorly and on the talus and calcaneus distally and posteriorly
  • eversion and/or pronation of the ankle and talus can injure the deltoid ligament
• lateral collateral ligament

  
  

  => is composed of three distinct bands that are commonly referred to as separate ligaments:

  • anterior talofibular ligaments - weakest and most commonly injured, can lead to anterolateral rotatory instability
  • posterior talofibular - stressed with dorsiflexion and ER
  • calcaneofibular ligament - stressed with dorsiflexion and inversion
  • anterior and posterior ligaments run in a fairly horizontal position
  • longer calcaneofibular ligament is nearly vertical
  • helps control inversion and/or supination of the ankle and talus
  • weaker and more susceptible to injury than MCL
• AXIS

  • in neutral ankle position, the joint axis passes approximately through the fibular malleolus and the body of the talus and through or just below the tibial malleolus
  • tibial torsion (or tibiofibular torsion) accounts for the toe-out position of the foot in normal standing

  => as tibial torsion increases, the axis of the ankle joint is positioned more laterally in the transverse plane

  • considered to have one degree of freedom, with dorsiflexion/plantarflexion occurring between the talus and the mortise
• Dorsiflexion


  Motion of the head of the talus dorsally (or upward) while the body of the talus moves posteriorly in the mortise
• Plantarflexion


  Opposite motion of the head and body of the talus
• Ankle joint

  • Primary motions allowed are dorsiflexion and plantarflexion
  • Normal ankle joint ROM is 20° for dorsiflexion and 50° for plantarflexion
• Dorsiflexion in weightbearing

  1. Tibia rotates over the talus

  2. Concave tibiofibular segment slides forward on the trochlear surface of the talus
• Because of the lower position of the fibular malleolus, the axis of the ankle is inclined 14° down on the lateral side
• Ankle joint in dorsiflexion

  • Wider anterior portion of the talus "wedges" into the mortise, separating the tibia and fibula to enhance stability
• Ankle joint in plantarflexion

  • Narrower posterior body of the talus is within the mortise
  • Ankle is less stable in plantarflexion, consistent with pattern of injury to lateral ankle ligaments
• Dorsiflexion of the foot around a typically inclined ankle axis

  1. Brings the foot up

  2. Brings it slightly lateral to the leg

  3. Appears to turn the foot longitudinally away from the midline
• Asymmetry in size and orientation of the facets means that the distal fibula moving on the larger lateral facet of the talus must undergo a greater displacement than the tibial malleolus during dorsiflexion
• SUBTALAR JOINT

  •also referred to as the “ talocalcaneal joint ”

  •a composite joint formed by three separate plane articulations between the talus superiorly and the calcaneus inferiorly providing a triplanar movement around a single joint axis

  •critical for dampening proximal rotational forces while maintaining contact of the foot with the ground
• Active or passive tension in the triceps surae


  Primary limitation to dorsiflexion
• Plantarflexion around the same single oblique ankle axis


  1. Foot goes down

  2. Moves medial to the leg

  3. Appears to turn the foot longitudinally toward the midline
• Dorsiflexion range of motion


  • Less range of motion seen with the knee extended compared to a knee in a flexed position
• Weight-bearing ankle dorsiflexion

  1. Tibia and fibula will move toward and medial to the foot

  2. Appear to rotate medially in the transverse plane
• Dorsiflexion limitation


  • Soleus and posterior talocrural joint capsule when the knee is flexed