Gross Anatomy
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FUNCTIONAL ANATOMY OF THE ANKLE AND FOOT

Required Reading: pages 688 - 713

I. INTRODUCTION (688 - 692)

  1. Popliteal Fossa - is a diamond shaped area locates behind the knee. This region contains important structures that pass from the thigh into the leg. The contents of this region include the following:
    1. Division of the sciatic nerve into ins 2 terminal branches, the tibial nerve and the common fibular ( peroneal) nerve. In addition, 2 cutaneous nerves originate in this area. The medial sural cutaneous branches from the tibial nerve while the lateral sural cutaneous branches from the common fibular nerve. These nerves supply the skin over the upper leg. They then unite to form the sural nerve that is cutaneous to the lower portion of the leg.
    2. The division of the popliteal artery into its terminal branches, the anterior and posterior tibial arteries. The pulse of the popliteal artery is difficult to locate but, with practice, can be palpated within the popliteal fossa.
    3. The termination of the anterior and posterior tibial veins into the popliteal vein.
    4. The short saphenous vein, a cutaneous vein, drains into the popliteal vein in the fossa and the popliteal lymph nodes can also be located near this termination.
  2. The Leg - The leg contains 2 bones that are connected to each other by a thick interosseous membrane. The tibia is the larger and more medial of the bones. It provides attachment for muscles of the leg and is also involved in weight bearing. The slender fibula plays only a minor role in weight bearing. The deep fascia divide the leg into 3 compartments: anterior, lateral and posterior. Each compartment contains muscles that act on the ankle joint and/or the joints of the foot ( tarsal joints) and the innervation to these muscles and the arteries supplying these muscles.
  3. The Foot - is made up of 7 tarsal bones, 5 metatarsal bones and the phalanges. The foot is arched longitudinally to help carry out the weight bearing function of the foot and transversely to help with movements of the foot. While the metatarsophalangeal joints and interphalangeal joints of the foot do play a role in movements of the lower limb, they will not be considered here. We will be concerned with the movements only at the tarsal joints. Plantigrade Movement is a property of the human foot. Movements of the foot are designed to adapt the sole of the foot to the ground even on uneven surfaces.
  4. The Ankle is a hinge joint comprised of the distal end of the tibia, the medial malleolus and the distal end of the fibula, the lateral malleolus . These bones articulate with the trochlea of the talus, one of the major tarsal bones.

COMPARTMENTS OF THE LEG (692-700)

  1. Anterior crural compartment
    1. Muscles
      1. Tibialis anterior
      2. Extensor hallucis longus
      3. Extensor digitorum longus
      4. Peroneus tertius
    2. Nerve
      1. Deep Fibular (peroneal)
      2. Motor - muscles of anterior compartment
      3. Sensory - skin between first 2 toes
    3. Artery
      1. Anterior tibial
        1. Muscular
        2. Malleolar
        3. Dorsalis pedis
    4. Function
  2. Lateral Crural Compartment
    1. Muscles
      1. Fibularis (peroneus) longus
      2. Fibularis (peroneus) brevis
    2. Nerve
      1. Superficial Fibular (peroneal)
      2. Motor - to muscles in lateral compartment
      3. Sensory - dorsum of foot
    3. 3. Artery
      1. None
    4. 4. Function (See Charts I & II)
  3. C. Posterior Crural Compartment
    1. Muscles
      1. Superficial Group
        1. Triceps Surae
          Gastrocnemius
          Soleus
        2. Plantaris
      2. Deep Group
        1. Popliteus
        2. Tibialis posterior
        3. Flexor digitorum longus
        4. Flexor Hallucis longus
    2. 2. Nerve
      1. a. Tibial
        1. i) Motor - to muscles in posterior compartment
        2. ii) Sensory - to posterior lateral aspect of leg, dorsal lateral aspect of the foot, and plantar surface of heel
    3. 3. Artery
      1. a. Posterior tibial
        1. i) Muscular
        2. ii) Malleolar
        3. iii) Peroneal
      2. b. Fibular (peroneal)
        1. i) Muscular
        2. ii) Malleolar
        3. iii) Perforating
    4. 4. Function (See Charts I & II)
  4. Collateral Circulation
    1. Cruciate Anastomosis
      1. Collateral circulation to leg and foot following blockage of femoral or popliteal arteries
      2. Deep Femoral
      3. Descending branch of lateral femoral circumflex a.
      4. Femoral
      5. Descending genicular artery
      6. Popliteal
      7. 5 genicular branches
      8. Anterior Tibial
      9. Recurrent branches
    2. Crural Anastomosis
      1. Collateral routes to foot following blockage of anterior or posterior tibial arteries.
      2. Anterior Tibial artery
      3. Medial & Lateral malleolar branches
      4. c. Dorsalis Pedis artery
      5. (1) Medial & lateral tarsal branches
      6. Posterior Tibial artery
      7. Malleolar branches
      8. Fibular (peroneal) artery
      9. Perforating branch
    3. Deep Plantar Arch of Foot
      1. Deep branch of Lateral Plantar artery
      2. b. Dorsalis Pedis artery
      3. Deep plantar artery

III. ANKLE JOINT (700 -704)

  1. Function - The ankle joint is a hinge type joint that participates in movement and is involved in lower limb stability. There are 2 types of motions that take place at the ankle joint : dorsiflexion and plantar flexion. Dorsiflexion involves bringing the dorsum of the foot towards to the anterior surface of the leg. Such movement is necessary in order to have the foot contact the ground heel first during heel strike and to allow the foot to clear the ground during the swing phase of gait. Plantar flexion occurs when the toes are in contact with the ground and the heel is raised off of the ground ( toe raises). This movement provides the propulsive force necessary to lifer the limb off of the ground and start it swinging forward during the toe off portion of gait. During midstance, when the lower limb supports the weight of the torso, the ankle is in its most stable configuration which is the dorsiflexed position.
  2. Bones
    1. Modified hinge joint between the following bones:
      1. Trochlea of the talus
      2. Lateral malleolus of fibula
      3. Medial malleolus of tibia
  3. Ligaments
    1. Deltoid
      1. Binds medial malleolus to tarsal bones
      2. Components
        1. Tibionavicular
        2. Tibiocalcaneal
        3. Tibiotalar
          anterior
          posterior
    2. Lateral
      1. Binds lateral malleolus to tarsal bones
      2. Components
        1. Talofibular
          anterior
          posterior
        2. Calcaneofubular
  4. Movement (See Charts 1 and 2 )
    1. Oblique axis for motion
      1. a. Posterior lateral portion of lateral malleolus
      2. b. Anterior medial portion of medial malleolus
    2. Terminology
      1. Flexion of forefoot occurs with extension of hind foot
      2. Terms dorsiflexion / plantar flexion used referring to movements at the ankle joint
    3. Dorsiflexion
      1. a. Bring dorsal surface of foot to anterior surface of leg
      2. Accomplished by muscles in anterior crural compartment
    4. Plantar flexion
      1. Brings plantar surface of foot away from leg pointing the toes towards ground
      2. Accomplished by action of superficial muscles in posterior crural compartment
  5. Joint Stability
    1. Most Stable Configuration
      1. a. Dorsiflexed position
    2. Properties
      1. Shape of Ankle Bones
        1. i) Trochlea tali wider anteriorly than posteriorly
        2. ii) Socket narrow posteriorly
      2. Function of Ligaments
        1. i) Interosseous membrane and Tibiofibular ligaments binds malleoli to trochlea
      3. Joint locked into stable configuration during dorsiflexion
  6. Role of Ankle Joint in Maintaining the Upright (Erect) Position
    1. Center of Gravity
      1. Falls in front of ankle joint
      2. Forces body to move forward at the ankle joint
      3. Ankle is forced into dorsiflexed position
      4. Ankle locked in stable ( dorsiflexed ) position
    2. Support of Ankle Joint
      1. Lack of ligamentous support anteriorly or posteriorly
    3. Muscle Activity
      1. Needed to maintain the ankle joint in neutral position
      2. Action of Triceps surae counterbalances force of gravity
        1. Gravity forces body forward dorsiflexing ankle joint
        2. Ankle joint stable in dorsiflexed position
        3. Triceps surae muscles plantar flex ankle joint
        4. Restrict amount of dorsiflexion at ankle joint during normal standing
  7. Injuries of the Ankle Joint
    1. Sprains
      1. Damage to ligamentous structures
      2. More common on lateral side of ankle
        1. Deltoid ( medial ) ligament strong
        2. Lateral ligaments weak
    2. Inversion Injuries
      1. Stress lateral side of ankle
      2. Result of excessive foot inversion
      3. Sprain lateral ligaments of ankle
    3. Eversion Injuries
      1. Stress medial side of ankle
      2. Result of excessive foot eversion
      3. Results in fracture dislocations

THE FOOT (705 - 714)

  1. Function - The foot plays an important role in supporting the weight of the entire body and in locomotion. The bones of the foot are arched longitudinally to help facilitate the support function . The transverse arch helps with movements of the foot . These movements help keep the sole (plantar surface) in contact with the ground despite the unevenness of the ground surface. They also work in concert with the ankle joint to help propel the foot off the ground during toe off portion of gait. It is convenient to speak of 3 segments of the foot: hindfoot , midfoot and forefoot. The calcaneus and talus comprise the hindfoot while the metatarsals and phalanges make up the forefoot. The navicular, cuboid and cuneiform bones make up the midfoot.
  2. Bones of the Foot
    1. Tarsal Bones
      1. Calcaneus
      2. Talus
      3. Navicular
      4. Cuboid
      5. Cuneiforms - Medial , intermediate, lateral
    2. Metatarsals (5)
    3. Phalanges
  3. Arches of the Foot
    1. Medial Longitudinal Arch
      1. Calcaneus , Talus , Navicular , Cuneiform (3), Metatarsals - 1,2,3
      2. Weight bearing
        1. Pronounced curve
        2. Weight transfer
          Calcaneus, metatarsal heads
    2. Lateral Longitudinal Arch
      1. Tuber calcaneus , Cuboid, Metatarsals 4 & 5
      2. Weight bearing
        1. Slight curve
      3. Weight transfer
        1. To ground
    3. Transverse Arch
      1. Cuneiform (3) , Cuboid, Base of metatarsals 1-5
      2. Concave arch
  4. Tarsal Joints - or intertarsal joints , are a complex of joints between the tarsal bones . These joints enable the forefoot to move in concert with the hind and midfoot . Movements at these joints are responsible for most of the important movements of the foot. The tarsal joints are synovial joints . These joints permit gliding and/or rotation movements.
    1. Subtalar joint - the talus articulates with the calcaneus at 3 different sites. A fairly large concavity the tarsal sinus separates these articulations into anterior and posterior portions. The posterior portion is called the subtalar joint. Within the sinus , a strong ligament, the talocalcaneal interosseous ligament is found. This ligament helps keep the 2 bones applied to each other during movements of the subtalar joint. Inversion and eversion of the heel occurs mainly at the subtalar joint.
    2. Transverse Tarsal Joints - are a combination of 3 separate joint spaces that include:
      1. Talocalcanealnavicular joint - consists of the anterior articulation between the talus and calcaneus and the Talonavicular articulation
      2. Calcanealcuboid joint
      3. Talonavicular
        Though they consist of separate joints, each with their own articular surfaces and separate joint capsules, we will consider the transverse tarsal joints as a single unit. Movements of the transverse tarsal joints enable the forefoot to move on the midfoot.
  5. Movements at the Tarsal Joints (See Chart III - Prime Movers of the Ankle and Tarsal Joints)
    1. The movements that take place at the tarsal joints can be confusing to understand. Movements of the joints are complex, almost as complex and confusing as the terminology used to describe them. To simplify matters, the following terminology will be used:
      1. The Neutral Position of the hindfoot occurs when the heel is aligned with the vertical axis of the tibia. That of the forefoot occurs when the base of the second metatarsal is aligned with the vertical axis of the tibia.
      2. Heel Inversion - refers to the movement at the subtalar joint. Heel inversion occurs when the heel ( calcaneus) deviates medially ( inward) from the vertical axis of the tibia. (Fig. 1)
      3. Forefoot Inversion occurs at the transverse tarsal joints. Forefoot inversion occurs when the second metatarsal deviates medially ( inward) from the vertical axis of the tibia. This movement also involves adduction of the forefoot.
      4. Heel Eversion - refers to the movement at the subtalar joint. Heel eversion occurs when the heel ( calcaneus) deviates laterally ( outward) from the vertical axis of the tibia. (Fig. 2)
      5. Forefoot Eversion occurs at the transverse tarsal joints. Forefoot eversion occurs when the second metatarsal deviates laterally ( outward) from the vertical axis of the tibia. This movement also involves abduction of the forefoot.
    2. Supination/Pronation occur primarily at the transverse tarsal joints and involve movements of the forefoot..
      1. Supination is a combination forefoot inversion and adduction occurring at the transverse tarsal joints. Supination occurs when the 1st metatarsal bone is elevated off the ground while the 5th metatarsal bone is depressed
      2. Pronation is a combination of forefoot inversion and abduction. Now, the 5th metatarsal is elevated while the 1st. metatarsal is depressed
  6. Plantar Ligaments
    1. Function of Plantar Ligaments
      1. Support tarsal joints
      2. Support bony arches
        1. "Fallen Arches"
          Loss of ligamentous support for bony arches
    2. Plantar calcaneonavicular ( Spring) ligament
      1. aBinds calcaneus to navicular bone
      2. Supports talocalcaneonavicular joint
      3. Main support for medial longitudinal arch
        1. Flattens when weight is placed on arch
        2. Springs back when weight is removed returning arch to original shape
      4. Weakness leads to fallen arches
    3. 3. Plantar calcaneocuboid ( Short plantar) ligament
      1. Binds calcaneus to cuboid bone
      2. Supports lateral longitudinal arch
    4. Long Plantar ligament
      1. Binds calcaneus to cuboid bone and base of metatarsal
      2. Supports lateral longitudinal arch
  7. Alignment of the Foot
    1. Pes Planus (Flat foot)
      1. Weak plantar ligaments
      2. Paralysis of peroneus longus
    2. Pes Cavus ( Exaggerated Arch)
      1. overactive peroneus longus
    3. Pes Varus
      1. Foot inverted and adducted
    4. Pes Valgus
      1. Foot everted and abducted

VASCULAR SUPPLY and INNERVATION OF THE FOOT(714 - 715; 719- 721)

  1. Dorsum
    1. Arterial Supply
      1. Dorsalis Pedis - is the continuation of the anterior tibial artery distal to the ankle joint
      2. Lateral tarsal br.
      3. Arcuate
      4. 1st. dorsal metatarsal artery
      5. Deep plantar
    2. Veins
      1. Dorsal venous arch
      2. Short saphenous vein
      3. Great saphenous vein
      4. Dorsalis pedis vein
    3. Innervation
      1. Deep Fibular Nerve
        1. Cutaneous to web space between 1st & 2nd toes
      2. Superficial Fibular Nerve
        1. Cutaneous to remainder of dorsum of foot
  2. Plantar Surface
    1. Posterior Tibial artery terminates as the medial and lateral plantar arteries
      1. Supply muscles and skin of plantar surface of foot
      2. Lateral plantar a. anastomoses with deep plantar branch of the dorsalis pedis to form deep plantar arch
    2. Tibial nerve terminates as medial and lateral plantar nerves
      1. Supply muscles and skin of plantar surface of foot

V. CLINICAL CONSIDERATIONS

  1. Actions of the Ankle and Tarsal Joints During Gait (Review the video "The Anatomical Gait Cycle")
    1. Acceleration and Heel Strike
      The ankle joint is in a neutral position to enable the heel portion of the foot to contact the ground prior to any other portion of the foot. the ground.
      1. Eccentric contractions of the muscles in the anterior crural compartment overcome the attempts of gravity to pull the ankle into a plantar flexed position.
    2. Heel Strike to Midstance
      The torso moves forward passively on the reference side as the limb on the opposite side of the body is in transition between toe off and acceleration. As a result , the reference ankle assumes a dorsiflexed position.
      1. Triceps surae muscles contract eccentrically to restrain the amount of passive dorsiflexion and also inverting the heel at the subtalar joint
        As the foot progresses from heel strike to midstance, inversion of the heel and supination of the forefoot places much of the body's weight on the lateral longitudinal arch of the foot. Supination of the forefoot "locks" the transverse tarsal joints aiding in this weight bearing function.
    3. Midstance to Toe Off
      The reference limb is preparing to leave the ground. This is the stage where concentric contractions of the gastrocnemius and soleus muscles begin to plantar flex the ankle joint and the heel is being readied to raise off of the ground. The foot undergoes a number of changes during this phase.
      1. Progression from midstance, the heel is everted at the subtalar joint and the forefoot pronated allowing the foot to be "loaded" as the weight of the body is transferred to the heads of the first 2 metatarsal bones.
      2. As the gastrocnemius and soleus become more active and the heel begins to come off the ground, the heel is inverted and the forefoot is supinated . The tarsal joints "lock" and the foot is turned into a rigid lever supporting the ability of the limb to transition from stance to swing phase.
    4. Toe Off to Acceleration
      The reference limb goes from a weight bearing to a non weight bearing position. The gastrocnemius and soleus muscles contract concentrically propelling the limb off of the ground as the reference limb enters the swing phase of gait.
      1. Ankle is actively plantar flexed .
  2. The Effect of Nerve Lesions on the Ankle and Tarsal Joints During Gait
    1. Common Fibular (Peroneal) Nerve
      1. Easily damaged as nerve winds superficially around the neck of the fibula.
      2. Drop foot / Foot slap
      3. Anterior crural muscles unable to contract eccentrically during interval between Acceleration and Heel Strike
      4. Fore foot rather than the heel strikes the ground during Heel Strike
      5. Patient produces a obvious "slapping" sound when going into Heel Strike
    2. Tibial nerve
      1. Inability to plantar flex ankle during interval between Toe Off and Swing
      2. Patient will not be able to do toe raises
    3. Segmental Innervation
      Movements at the ankle and tarsal joints provide means to determine which segments (roots) of the Lumbosacral may be damaged.
      1. L 4
        1. Inversion of subtalar joint
      2. L 5
        1. Dorsiflexion of ankle
      3. S1
        1. Plantar flexion of ankle
        2. Eversion of subtalar joint


CHART I MUSCLES OF THE LEG

MUSCLE JOINT(S) ACTION(S) NERVE SEGMENT
Anterior Compartment:
Tibialis Anterior Ankle

Transverse Tarsal

Dorsiflex

Supinate

Deep Fibular (Peroneal) L 4, 5 S 1
Extensor Hallucis Longus Ankle Dorsiflex Deep Fibular (Peroneal) L 4, 5 S 1
Extensor Digitorum Longus Ankle Dorsiflex Deep Fibular (Peroneal) L 4, 5 S 1
Fibularis Tertius Ankle

Transverse Tarsal

Dorsiflex

Pronation

Deep Fibular (Peroneal) L 4, 5 S 1
Lateral Compartment:
Fibularis (peroneus) Longus Subtalar

Transverse Tarsal

Eversion

Pronation

Superficial Fibular (Peroneal) L 4, 5 S 1
Fibularis (peroneus) Brevis Subtalar

Transverse Tarsal

Eversion

Pronation

Superficial Fibular (Peroneal) L 4, 5 S 1
Posterior Compartment:
Popliteus Knee Unlocks Tibial L 4, 5 S 1
Gastrocnemius Knee

Ankle

Subtalar

Flexion

Plantar flexion

Inversion

Tibial S 1,2
Soleus Ankle

Subtalar

Plantar flexion

Inversion

Tibial S 1,2
Plantaris Ankle Plantar flexion Tibial L5,S1
Tibialis Posterior Transverse Tarsal Supination Tibial L 4, 5 S 1
Flexor Digitorum* Longus Ankle

Transverse Tarsal

Plantar flexion

Inversion

Tibial L 4, 5
Flexor Hallucis* Longus Ankle Plantar f lexicon Tibial L 4, 5
* Weak ankle plantar flexors. Act mainly on the toes



CHART II PRIME MOVERS OF THE ANKLE & TARSAL JOINTS

MOVEMENT JOINT MUSCLES NERVE SEGMENT
Dorsiflexion Ankle Tibialis Anterior Deep Fibular (Peroneal) L 4, 5 S 1
Extensor Hallucis Longus Deep Fibular (Peroneal) L 4, 5 S 1
Extensor Digitorum Longus Deep Fibular (Peroneal) L 4, 5 S 1
Fibularis Tertius Deep Fibular (Peroneal) L 4, 5 S 1
Plantar flexion Ankle Gastrocnemius Tibial S 1, 2
Soleus Tibial S 1, 2
Plantaris Tibial L5,S 1, 2
Inversion Subtalar Tibialis Anterior Deep Fibular (Peroneal) L 4, 5 S 1
Tibialis Posterior Tibial L 4, 5 S 1
Eversion Subtalar Fibularis (peroneus) Longus Superficial Fibular (Peroneal) L 4, 5 S 1
Fibularis (peroneus) Brevis Superficial Fibular (Peroneal) L 4, 5 S 1
Pronation Transverse Tarsal Fibularis (peroneus) Longus Superficial Fibular (Peroneal) L 4, 5 S 1
Supination Transverse Tarsal Tibialis Anterior Deep Fibular (Peroneal) L 4, 5 S 1
Tibialis Posterior Tibial L 4, 5 S 1


Figure 1 - Bones of the Foot
Name the lettered bones and numbered joints of the foot. Be able to identify the type of joint indicated at each number and the movements that occur there.


Fig. 2 Movements of the Foot - Inversion and Eversion of the Heel
The neutral position of the heel occurs when the tuber calcaneum ( back of the heel) is aligned with the vertical axix of the tibia. Inversion involves moving the back of the heel towards the midline while Eversion involves moving the heel laterally. Both movements take place at the subtalar joint


Fig. 3 Movements of the Foot - Forefoot Eversion and Inversion
The neutral position of the forefoot occurs when the base of the second metatarsal is aligned with the vertical axis of the tibia. Inversion involves moving the second metatarsal and the forefoot towards the midline while eversion involves moving the second metatarsal and the forefoot laterally. Both movements take place at the transverse tarsal joints


Fig. 4 Plantar Surface of Foot
1. Name and give the functions of the joints to which the arrows are pointing.

2. Name the bones and parts of bones indicated by the letters and numbers.

3. Draw in the main plantar ligaments


OBJECTIVES

  1. Learn the contents of the three muscular compartments of the leg including the nerve and blood supply to each .
  2. Know the collateral circulatory routes that comprise the following:
    1. Cruciate anastomosis
    2. Ankle anastomosis
    3. Deep plantar arch
  3. Know the bony and ligamentous structures that comprise the ankle and foot
  4. Be able to identify the bones participating in the formation of the ankle joint
  5. Be able to identify the bones participating in the formation of the tarsal joints joint
  6. Understand the role ligaments play in providing support for the ankle and tarsal joints
  7. Be able to explain the stable configuration of the ankle joint and the factors that promote ankle stability
  8. Know the proper alignment of the ankle and foot
    1. Understand the anatomical basis for foot deformities
  9. Know the attachments, innervation and primary action(s) of the muscles acting on the ankle and tarsal joints.
  10. Understand the types of movements that can take place at the ankle and tarsal joints
  11. Know the muscles responsible for producing each movement
  12. Be able to determine the site of peripheral nerve lesions based upon deficits in movements at the ankle and tarsal joints
    1. Be able to differentiate between how peripheral nerve lesions effect the ankle and tarsal joints from a lesion to a specific root of the lumbosacral plexus
    2. Learn how to test for the integrity of the prime movers of the ankle and tarsal joints
  13. Understand the position of the ankle joint and tarsal joints during normal gait . Be able to determine how the forces acting on these joints result in the configuration seen at each portion of the cycle.
  14. Know how peripheral nerve and /or nerve root lesions will affect the functioning of the ankle and foot during gait
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