Ankle and Foot Structure & Function Notes

Ch. 11: Structure & Function of the Ankle and Foot

Objectives

• Describe the connective tissues of the ankle and foot.

• Describe the primary motions that occur at the talocrural, subtalar, and transverse tarsal joints.

• Describe the most stable position of the talocrural joint.

• Describe the planes of motion and axes of rotation for dorsiflexion/plantarflexion, inversion/eversion, and adduction/abduction.

• Cite components of motions of pronation and supination.

• Explain the function of the medial longitudinal arch.

• Explain why the lateral ligaments of the ankle are injured far more often than the medial ligaments.

• Describe common abnormal gait patterns involved with weakness of the dorsiflexor muscles.

Brief Overview of the Gait Cycle

• Walking is also referred to as gait.

• Gait cycle: describes the events that occur (while walking) within two successive heel contacts of the same leg.

• Each gait cycle is divided into two phases: a stance and swing phase.

  • Stance Phase: refers to the events that occur when the foot is in contact with the ground.

    • Divided into five events: (1) heel contact, (2) foot flat, (3) mid stance, (4) heel off, and (5) toe off.

  • Swing Phase: describes the events that occur when the foot is swinging through the air, advancing the lower extremity to the next step.

    • Divided into three events: (1) early swing, (2) mid swing, (3) late swing.

Traditional Gait Cycle

The traditional gait cycle consists of the following events and periods:

• Events: Heel contact (0%), Foot flat (8%), Mid stance (30%), Heel off (40%), Toe off (60%), Early swing (75%), Mid swing (85%), Late swing (100%).
  Note the events and their order for the exam.

Ranchos Los Amigos Gait Cycle

• Another gait cycle definition involves any part of the feet making contact with the ground.

Terminology

• Plantar: aspect of the foot refers to the sole or its bottom.

• Dorsal: aspect of the foot refers to the top or its superior portion.

• Rearfoot, midfoot, and forefoot are commonly used clinical terms.

  • Use anterior/posterior

  • Use dorsal or plantar for comparison

Osteology

• The foot consists of 7 tarsals, 5 metatarsals, and 14 phalanges.

• The distal tibia and fibula are also part of the ankle joint.

• Fibular notch: small, concave portion of the distal tibia that articulates with the fibula, forming the distal tibiofibular joint, which is stabilized by the interosseus membrane and the anterior and posterior tibiofibular ligaments.

• Tibiofibular joint: stabilizes the rectangular concavity to accept the talus bone, forming the talocrural joint (ankle).

• Tarsal bones: talus, calcaneus, navicular, cuboid, and the medial, intermediate, and lateral cuneiforms.

  • Ankle joint = talocrural joint.

  • The talus is convex.

  • The distal tibia and fibula are concave.

Tarsal Bones

• Rearfoot

  • Talus, calcaneus

• Midfoot

  • Navicular

  • Medial cuneiform, intermediate cuneiform, and lateral cuneiform

  • Cuboid

• Forefoot

  • Metatarsals

  • Phalanges

Remembering the Tarsal Bones

• A. Calcaneus

• B. Talus

• C. Navicular

• D. Medial cuneiform

• E. Intermediate cuneiform

• F. Lateral cuneiform

• G. Cuboid

Arthrology of the Ankle & Foot

The arthrology of the ankle and foot consists of the following joints:

• Talocrural joint

• Subtalar joint

• Transverse tarsal joints

• Tarsometatarsal joints

• Metatarsophalangeal joints

• Interphalangeal joints

• Ankle joint

• Division line between tarsal bones

Proximal Joints of the Ankle and Foot

• Talocrural: allows motion in the sagittal plane – dorsiflexion and plantarflexion.

• Subtalar: allows an oblique arc of motion that results primarily in combined motions of inversion and adduction, or eversion and abduction (2 components of pronation and supination).

• Transverse tarsal: permits the most oblique motion through all 3 planes – purest pronation and supination.

  • No rotation allowed

Joint Motions/Kinematics

The following joint motions and kinematics are important:

• Dorsiflexion

• Plantar Flexion

• Inversion: raising medial border

• Eversion: raising lateral border

• Adduction

• Abduction

• Pronation: a fundamental movement includes eversion, abduction, and dorsiflexion.

• Supination: a fundamental movement of inversion, adduction, and plantarflexion.

  • Pronation: Eversion, Abduction, Dorsiflexion

  • Supination: Inversion, Adduction, Plantar Flexion

Kinematics Cont’d

• Dorsiflexion and Plantarflexion occur in the sagittal plane about a medial-lateral axis of rotation.

• Inversion and Eversion occur in the frontal plane about an anterior-posterior axis of rotation.

• Abduction and adduction occur in the transverse plane about a vertical axis of rotation.

• Occur most regularly at the subtalar and transverse tarsal joints.

• Pronation – combination of eversion, abduction and dorsiflexion of any region of the ankle and foot.

• Supination – combination of inversion, adduction, and plantarflexion.

Pronation and Supination

• Pronation involves the transverse tarsal and subtalar joints.

• Supination also involves the transverse tarsal and subtalar joints, and is aided by the tibialis posterior.

Talocrural Joint

• Commonly called the ankle joint.

• Articulation between the trochlea of the talus and the concavity formed by the distal tibia and fibula (mortise).

• Stability maintained by:

  • Tight fit of talus in the mortise.

  • Collateral ligaments and muscles.

  • Strength of the distal tibiofibular joint.

• Mortise joint = ankle joint.

• Open pack for ankle plantar flex.

• Close pack = dorsiflex.

Kinematics of Talocrural Joint

• Talocrural Joint: 1 degree of freedom, permits dorsiflexion and plantarflexion of the ankle.

• Essential for forward progression of movement while walking and squatting motions.

• Arthrokinematics: convex trochlea of the talus within the fixed concave mortise.

  • Talus = convex

  • Fibula and tibia = concave

  • Rule # 1 Roll and slide in opposite directions

  • Use anterior and posterior for roll and glide

  • Roll is posterior and slide inferior

  • Open Chain = Rule 1

Subtalar Joint

• Located at the rearfoot.

• Consists of the articulation between the facets on the inferior surface of the talus and the matching facets on the superior surface of the calcaneus.

• The shape of joint is specifically designed to allow frontal and horizontal plane of motions between the foot and the lower leg.

• Essential for adapting to uneven ground surfaces or cutting laterally or medially while walking or running.

Kinematics of Subtalar Joint

• Allows the combined motions of inversion/adduction and eversion/abduction of the rearfoot.

• The rotary (horizontal plane) motions are adduction and abduction.

• The motions involve the calcaneus moving underneath the fixed talus, which occurs when the foot is off the ground.

• When the foot encounters uneven ground, the response is that the calcaneus rotates while allowing the leg to remain vertical.

Transverse Tarsal Joint

• Separates the rearfoot from the midfoot.

• Consists of the talonavicular joint and the calcaneocuboid joint.

• Provides the purest form of pronation and supination and allows the midfoot to move independently of the rearfoot.

• This allows the foot to conform to many different terrains while walking or running.

  • Highly mobile in different terrains (sand, concrete)

  • 3 degrees of freedom

Distal Joints of the Foot

• Tarsometatarsal joints

  • Formed by the base of metatarsals with the 3 cuneiforms and the cuboid

• Metatarsophalangeal joints (MTP)

  • Formed by the convex head of metatarsals and concave proximal phalanx

• Interphalangeal Joints

  • Great toe 1 IP only

Supporting Structures of Talocrural Joint

• Interosseous membrane - binds tibia to fibula; provides stability to the distal tibiofibular and talocrural joints.

• Anterior and posterior tibiofibular ligaments – binds the distal tibiofibular joint, improving the stability of the mortise.

  • Injury to these ligaments often involved in a “high-ankle” sprain

• Deltoid ligament – limits eversion

  • triangular-shaped ligament originating off the medial malleolus. Contains three sets of fibers: tibionavicular, tibiocalcaneal, and tibiotalar

• Lateral collateral ligaments – limits inversion

  • Anterior talofibular ligament

  • Calcaneofibular ligament

  • Posterior talofibular ligament

• Inside of the ankle are medial structures.

• Inversion injuries are more common.

• Everything lateral.

• Everything medial.

Open vs. Closed Pack Position

• Closed pack position of the talocrural joint – full dorsiflexion.

  • Ankle is the most stable because most of the collateral ligaments and all the plantar flexor muscles are stretched.

  • Further stabilized as the trochlea becomes wedged into the mortise.

• Open packed position – full plantar flexion – most unstable position.

  • Slackens most of the collateral ligaments and all the plantar flexor muscles.

  • Mortise loosens its grip on the talus.

• Sprains and strains ligaments and tendons.

• More fractures.

Calcaneal Position

• Neutral

• Calcaneal valgus

  • Distal segment away from midline

• Calcaneal varus

  • Distal segment toward midline

  • Calcaneus is closer together (Valgum) and ankle is more out (lateral)

• Calcaneus Valgus = Flat foot or pronated foot

Arches

• Foot must be able to:

  • Absorb shock

  • Adjust to changes in terrain

  • Propel the body forward

• Three Arches:

  1. Medial longitudinal arch

  2. Lateral longitudinal arch

  3. Transverse arch

Help jump. Flat foot can’t jump. Flat foot have knee problems.

Medial Longitudinal Arch (Instep)

• Primary shock absorbing structure of the foot.

• Supported by non-muscular structures:

  • Ligaments

  • Joints

  • Plantar fascia

• Arch normally lowers slightly during the early stance phase, allowing the foot to gradually accept body weight (Subtalar everts).

• Lowering of arch and eversion are controlled by eccentric activation of invertor muscles.

• Eventually, the arch rises in preparation for push-off. The raised arch with inversion helps to convert the foot into a more stable structure.

  • Arch lower slightly in early stance phase.

  • Accept more Body weight on plantar fascia, which can cause plantar fasciitis.

Pes Planus

• Associated with an over-stretched and weakened plantar fascia, as well as an over-pronated subtalar joint.

• A person with this condition must often rely on active muscle forces produced by intrinsic and extrinsic muscles of the foot to support the arch.

• Could lead to fatigue, heel spurs, and plantar fasciitis.

  • Tight calf’s produce heel spurs because the Achilles tendon pull calcaneus.

  • Anatomical term for a flat foot.

Lateral Ankle Joint Ligaments

• Anterior talofibular ligament

• Calcaneofibular ligament

• Posterior talofibular ligament

Medial Ankle Joint Ligaments

• Make up the deltoid ligament

• Tibionavicular portion

• Tibiocalcaneal portion

• Posterior tibiotalar portion

• Anterior tibiotalar (deep)

Lateral Ankle Sprains

• One of the most common injuries of the lower extremity.

• Involves an inversion sprain of the ankle and foot.

• Often associated with damage to lateral ligaments.

  • The anterior talofibular ligament is most sprained or torn, mechanism of injury is plantar flexion and inversion.

• To improve ankle stability – co-contraction activities is a great way to improve performance, stability, and strength.

  • Form of isometric exercise that focuses on agonist/antagonist or synergist muscles that stabilizes the joint.

• If you jump, don’t land in plantar flexion because it can cause a co-contraction (isometric activity on the muscles around the ankle joint to help stabilize the joint).

Ankle Bursa

The ankle contains the retrocalcaneal bursa and the subcutaneous calcaneal bursa.

Extrinsic vs. Intrinsic Muscles of the Foot and Ankle

• Extrinsic – have their origin proximal to the ankle joint on the femur, tibia, or fibula.

  • Found in the 3 compartments of the leg:

    • Anterior compartment

    • Lateral compartment

    • Posterior compartment

  • Each compartment is innervated by a different nerve that arises from the sciatic nerve.

• Intrinsic – both origin and insertion are distal to the ankle joint.

Anterior Compartment Muscles

• Tibialis anterior – paralysis or weakness of this muscle may result in “foot drop” while in the swing phase of gait.

• Extensor digitorum longus – may result in tightness, spasticity, or overuse of this muscle may result in a “claw toe” deformity of toes 2-5 (hyperextension of MTP and flexion of the PIP and DIP joints).

• Extensor hallucis longus

• Fibularis tertius

• All muscles are innervated by the deep fibular nerve, and all perform dorsiflexion as their primary actions.

  • Stroke pt with spasticity.

Tibialis Anterior & Fibularis Tertius

• The foot is dorxiflexed when taking the first step.

• On the swing phase, the foot has to be in isometric dorxiflexion contraction.

• Foot drop = dragging foot.

• Tibialis anterior dorsiflexes.

Clinical Signs of Weakness of the Dorsiflexor Muscles: “Foot Drop” versus “Foot Slap”

• Dorsiflexors of the ankle have two important functions during gait:

  • During the swing phase, the dorsiflexors contract, elevating the foot to clear the ground.

  • At the early stance phase, the dorsiflexors are activated eccentrically to slowly lower the sole of the foot to the ground.

• Injury to the deep fibular nerve can cause paresis (weakness) or paralysis of the muscles.

• Foot drop: describes a condition in which the foot drops into plantar flexion as the leg is advanced during the swing phase of gait.

  • Tibialis anterior paralysis = foot slack decision - TA can’t control the descent of foot.

  • Paralysis

  • Foot slap paralysis of TB

  • Foot drop is weakness of TB

  • = paralysis TB = weakness of TB

Common Ankle and Foot Pathologies

• Shin Splints: pain on the medial side of the tibia, an overuse injury caused by running on toes or hard surfaces or jumping sports.

  • Often involves inflammation of the dorsiflexors and affects runners.

  • Excessive pronation of the foot during running or walking may worsen the condition.

• Posterior shin splints = gastroc

• Anterior shin split = side or medial of tibialis anterior

• Calf preventing full mobility

• Inflammation of the dorxiflexion because of overuse

Lateral Compartment Muscles

• Fibularis longus

• Fibularis brevis – tendon of muscle is commonly involved with an avulsion fracture of the process of the styloid process of the 5th metatarsal – dancer’s fracture can occur after a strong activation of this muscle to break an excessive inversion movement of ankle.

• Primary plantar flexors and evertors.

• Not a trauma fracture, but rather a muscle pulling on the bone too hard and causing a fracture = avulsion fraction.

Posterior Compartment Muscles

• Gastrocnemius

• Soleus – extends the knee in closed-chain while plantarflexing foot.

• Plantaris

• Tibialis posterior – provides essential support to the medial longitudinal arch. A ruptured tendon causes traumatic pes planus.

• Flexor digitorum longus – spasticity or tightness may result in a posture of plantar flexion of the ankle, inversion, and flexion of the toes.

• Flexor hallucis longus

• All flexors on the back.

Selective Stretching Between Soleus and Gastrocnemius

• Gastroc: Knee extended and dorsiflexed ankle.

  • For the stretch to be effective, the muscle must be stretched in the opposite of ALL actions.

• Soleus: knee flexed and dorsiflexed ankle.

  • Having the knee bent results in gastrocnemius becoming passively insufficient – resulting in putting the muscle in a slackened position.

• Stretch - do the opposite of all its actions

• Soleus= posterior aspect of tibialis

• Soleus = only crosses one joint (Ankle joint)

Intrinsic Muscles of the Foot

Dorsum of Foot

• Extensor digitorum brevis – extension of toes minus 5th toe

• Dorsal interossei – abduction of the 2nd to 4th toes

Plantar Surface

• First layer

  • Flexor digitorum brevis – flexion of MTP and PIP of lesser 4 toes

  • Abductor hallucis

  • Abductor digiti minimi

• Second layer

  • Lumbricals – flexion of MTP joints while extending IP joints

• Third layer

  • Adductor hallucis – flexion and adduction of MTP joint of great toe

  • Flexor hallucis brevis

  • Flexor digiti minimi

• Fourth layer

  • 4 dorsal interossei – abduction 2-4 toes

  • 3 plantar interossei – adduction of toes

Equinus Foot and Calcaneus Foot

• Equinus foot: hindfoot fixed in plantar flexion.

• Calcaneus foot: hindfoot fixed in dorsiflexion.

• Head of metatarsals would be compared to knuckles.

• Very rare.

Pes Cavus and Pes Planus

• Pes Cavus: abnormally high arch.

• Pes Planus: abnormally flat foot.

Flat foot. Valgum.

Pronated Foot and Flat foot

• Pronation of the foot and ankle during the stance phase of gait is essentially a temporary collapse of the ankle, rearfoot, and midfoot.

• Excessive pronation has been linked to lower limb overuse injuries, congenital defects, developmental defects, Equinus, excessive external rotation of the hip.

• A patient with little or no longitudinal arch. A flatfoot is said to be flexible if the arch can be re-created with the patient standing on toes.

• On the contrary, a rigid flatfoot (rare) positions the calcaneus in a valgus position and the midtarsal pronated. Results in the navicular becoming displaced.

• Flexing helps curve arch.

Morton’s Neuroma

• Abnormal pressure on the plantar digital nerve commonly seen at the webspace of the 3rd and 4th metatarsals.

• Elevated heel squats are active insufficiency for quads.

• Wearing the wrong size of shoes (smaller) can cause toes to go inward (adduction) of 3 and 4th metatarsal.

Turf Toe

• Forced hyperextension of the great toe at MTP joint. Common in soccer, football, and baseball players.

• MTP sprain.

• Cletus shoes

Hallux valgus

• Also known as a bunion.

• Lateral or valgus deformity of the great toe – first metatarsal and it involves the entire ray.

• Has been observed to occur almost exclusively in populations that wear shoes.

• Weakening of the MCL may lead to subluxation of the proximal phalanx.

Valgus.

Claw toe/hammer toe/Mallet toe

• Claw toe: Dorsiflexion of the MTP joint and plantarflexion of the DIP and PIP joint.

• Hammer toe: MTP joint is dorsiflexed or neutral, PIP is plantarflexed, DIP is hyperextended or plantar flexed.

• Mallet toe: MTP and PIP joint are neutral, and DIP is plantarflexed.

Avulsion Fracture of 5th Metatarsal Styloid Process

• Also known as a dancer’s fracture – occurs after strong contraction of peroneus/fibularis brevis tendon that tears the tendon and styloid process off the 5th metatarsal.

Plantar Fasciitis

• Painful condition that involves inflammation of the plantar fascia of the foot. Associated with recreational activities that place repetitive stress on plantar fascia (runners, jumpers, tennis players).

• Rising on toes or pushing off while running or jumping by strong activation of plantar flexors.

Key Muscles

• L4: gluteus medius, TFL, hamstrings, tibialis anterior

• L5: weak glute maximus, long toe extensors, tibialis posterior

• S1: glute max, ankle plantar flexors

Quiz Questions!

1. Which of the following positions is considered the close-packed, most stable position of the talocrural joint?

   • a) Full abduction

   • b) Full adduction

   • c) Full dorsiflexion

   • d) Full plantarflexion

The answer is full dorxiflexion because it causes the wider anterior part to the talus

2. The primary motions that occur at the talocrural joint are:

   • a) Dorsiflexion and plantarflexion

   • b) Inversion and eversion

   • c) Adduction and abduction

   • d) Pronation and supination

3. The combined action of dorsiflexion, eversion, and abduction is described as _ of the ankle and foot.

   • a) Supination

   • b) Pronation

   • c) Hyperextension

   • d) Varus

4. A muscle that courses posterior to the medial-lateral axis of rotation of the ankle can be predicted to produce which of the following actions?

   • a) Dorsiflexion

   • b) Plantarflexion

   • c) Inversion

   • d) Eversion

5. One of the primary functions of the longitudinal arch is to:

   • a) Limit excessive supination of the foot

   • b) Help safely absorb weight-bearing forces through the foot

   • c) Prevent excessive plantar flexion at the talocrural joint

   • d) Prevent excessive flexion at the lateral four metatarsophalangeal joints

6. Injury to the tibial nerve most likely will result in weakness of which of the following actions?

   • a) Dorsiflexion

   • b) Eversion

   • c) Extension of digits 1 – 4

   • d) Plantarflexion

Tibial nerve innervates the posterior part of the leg which includes muscles of Plantar Flexion Gastrocnemius Soleus and tibialis anterior Fibular or Peroneal Nerve