Ankle and Foot Kinematics, Pathologies, and Gait Analysis

What is the significance of the oblique axis in ankle movements?

Most movements occur in an oblique axis, which is not adequately defined by standard movement terminology.

DF/PF

sagittal plane/medial-lateral axis

inversion/eversion

frontal plane

adduction and abduction

Horizontal plane

What is the definition of Pronation in terms of ankle movement?

Pronation is defined as Dorsiflexion (DF) + Eversion (Ev) + Abduction (Abd).

Mortise maintained by

Ligaments that bind tibia and fibula

Deltoid ligament provides

multi-directional rotary stability to the mortise

talocrural joint

convex: talus

concave: tibia and fibula

Fundamental Ankle Movements

DF PF

SUP/Pro

Add/Abd

Fundamental terminology

Defines movement of the foot or ankle as occurring at right angles to the three standard axes of rotation

abduction/adduction of ankle

Horizontal plane

What is the definition of Supination in terms of ankle movement?

Supination is defined as Plantarflexion (PF) + Inversion (Inv) + Adduction (Add).

2/3 of all lateral ligament injuries

Involve both CFL and ATFL

What is the shape and function of the Talocrural Joint (TCJ)?

The TCJ has a 'mortise' shape, concave proximally, providing natural stability and transmitting 90-95% of compressive force through the Talus and Tibia when standing.

talocrural axis of rotation

Runs through both malleoli

DF associated with

Eversion and ABduction

What role does articular cartilage play in the TCJ?

Articular cartilage protects the subchondral bone and is 3mm thick, compressing during peak physiological loads.

Why are injuries to the medial ligament uncommon?

due to the strength of the Deltoid ligament and the lateral malleolus blocking excessive eversion.

Deltoid ligament injury

Abduction and ER or extreme eversion

Associated injuries of deltoid ligament

trauma to the distal tib/fib joint, lateral ligaments, and spring ligaments

CFL during dorsiflexion

Taut

CFL resists

inversion, especially during full dorsiflexion.

What causes injury to the ATFL?

excessive inversion combined with horizontal plane adduction and plantarflexion.

What does the Posterior Talofibular Ligament (PTFL) do?

The PTFL stabilizes the talus in the mortise and limits abduction and external rotation of the talus, particularly when dorsiflexed.

Talocrural osteokinematics

DF and PF

How do PF and DF relate to the movement of the talus?

PF and DF are linked to the anterior and posterior translation of the talus within the mortise.

What percentage of ankle sprains involve lateral ligament injuries?

80% of all ankle sprains are associated with one or more injuries to the lateral ligaments.

Talocrural neutral

90 degrees

Talocrural closed chain movement

Mortise moves on talus

What is the mechanism behind a typical ankle sprain?

slight inversion of the calcaneus during initial contact, with the medial malleolus unable to block the medial side of the mortise.

Calcaneovalgus

>180

Calcaneovarus

<180

How do CFL and ATFL contribute to ankle stability?

resist most ankle dorsiflexion and plantarflexion movements.

ATFL and anterior capsule during PF

Tighten

TCJ during LR

Leg dorsiflexes over talus

Push off during gait TCJ

CPP, most stable

During walking, pronation and supination occur in the

Horizontal plane

subtalar neutral

⅓ from full eversion ⅔ from full inversion

TCJ dorsiflexion arthrokinematics

Talus rolls anteriorly and slides posteriorly.

What happens to the ATFL and anterior capsule during dorsiflexion?

They go slack.

What is calcaneovalgus?

A medial increase in angle where the distal segment moves away from the midline.

Forefoot valgus

eversion of forefoot

Forefoot varus

Inversion of forefoot when subtalar joint in neutral

Plantarflexion arthrokinematics

Talus rolls posteriorly and slides anteriorly.

Choparts joint

transverse tarsal joint

Most versatile foot joint

TTJ

TTJ motions

Eversion, inversion, abduction & dorsiflexion, adduction & plantar flexion

Talonavicular joint

convex head of talus and concave proximal navicular (anterior joint)

What are the two parts of the transverse tarsal joint (TTJ)?

Talonavicular joint and calcaneocuboid joint.

What is the role of the CFL and posterior capsule during plantarflexion?

They slacken.

What occurs during initial contact (IC) in gait?

Rapid plantarflexion to lower the foot to the ground.

What is the significance of heel off in gait mechanics?

The anterior talus wedges into the mortise, causing the distal tib/fib to spread apart.

What stabilizes the dorsiflexed ankle during push-off?

Tension in the distal tib/fib ligaments and interosseous membrane.

What is the primary motion of the subtalar joint (STJ) when non-weight bearing (NWB)?

The calcaneus moves.

What does subtalar pronation involve?

Calcaneal eversion.

What does subtalar supination involve?

Calcaneal inversion.

What is the axis of rotation (AoR) for the subtalar joint?

It pierces through the lateral posterior heel.

What is the clinical significance of subtalar neutral?

Used for orthotic fabrication, defined as the line bisecting the aligned posterior leg and calcaneus.

What is calcaneovarus?

A decrease in angle where the distal segment moves toward the midline.

What is forefoot varus?

A sustained TMT supination twist that occurs when the hindfoot is pronated and weight-bearing.

What type of motion does the talonavicular joint provide?

Mobility to the medial column of the foot.

What are the main motions of the talonavicular joint?

Twisting (inversion/eversion) and bending (flexing/extending).

What is the role of the spring ligament in the talonavicular joint?

Forms the floor and medial wall of the joint, and tears can result in flat foot.

How does the calcaneocuboid joint differ from the talonavicular joint?

It is inflexible and resists sliding, providing stability to the lateral column of the foot.

What are the three key points regarding TTJ kinematics?

1. It has 2 separate axes of rotation. 2. Amplitude & direction of movement differ during WB compared to NWB. 3. Kinematics functionally influenced by subtalar joint position

What influences kinematics in the subtalar joint?

The position of the subtalar joint.

Oblique axis runs

Vertical and M-L

What motions occur in the longitudinal axis of the foot?

Eversion and inversion.

What is the function of the oblique axis in the foot?

It allows for abduction + dorsiflexion and adduction + plantarflexion.

How do functional kinematic movements occur in the foot?

They occur as a blending of both the longitudinal and oblique axes.

What is the relationship between supination and pronation in the midfoot?

The midfoot allows for twice as much supination as pronation.

Which muscle is the prime supinator of the foot?

The posterior tibialis.

Tibialis posterior during unloaded supination

contributes to the spin of the navicular on the talus which raises the medial longitudinal arch

What is the role of the rigid calcaneocuboid joint during inversion?

It allows the inverting and adducting calcaneus to pull the lateral column under the medial column.

•If calcaneus is fixed, pronation and supination occur primarily at

Talonavicular joint from a spin motion

What joint serves as the pivot point for navicular spin?

The talonavicular joint.

Loaded IR at the leg + proration at the TTJ and SCJ can cause

Supinate the forefoot

Pronate rearfoot

What happens during unloaded pronation in the foot?

The fibularis longus lowers the medial foot and raises the lateral foot.

Rearfoot receives 2x as much pressure as the

Forefoot

Pressure on the forefoot is greatest at the

2nd and 3rd met heads

What is the primary load-bearing structure of the foot?

The medial longitudinal arch.

What bones comprise the medial longitudinal arch?

Calcaneus, talus, navicular, cuneiforms, and three medial metatarsals.

Plantar fascia & intrinsics absorb body weight and keep

The arch from flattening

As the arch lowers during Wb

The rearfoot goes into slight pronation

What other structures provide support to the medial longitudinal arch?

Fat pads, sesamoids in the great toe, and plantar fascia.

What is the keystone of the medial longitudinal arch?

The talonavicular joint.

How does body weight affect the medial longitudinal arch during standing?

It pushes the talus inferiorly, slightly lowering the arch.

Principle joint for inversion and eversion

STJ

SCJ and TTJ during early stance

Pronation

Talocrural joint during IC

Rapidly plantarflexes to lower forefoot to the ground

What is the normal navicular tuberosity drop during weight-bearing?

7mm.

Chronic pronation causes

The tibia to IR and it drags the femur into IR also

What occurs to the medial longitudinal arch during the loading response of gait?

It lowers and becomes more flexible.

Excessive pronation can also cause

Rearfoot varus

Lower leg IR causes

Knee valgus

What happens to the subtalar joint during the first 30-35% of the gait cycle?

It pronates (everts) to allow for flexibility.

What occurs during late stance in the gait cycle?

The medial longitudinal arch rises and the subtalar joint supinates.

What are the two mechanisms of subtalar pronation during stance?

1. Calcaneal eversion from ground reaction force. 2. Tib-fib internal rotation.

STJ and TTJ Transition from pronation to supination occurs when

At around 30-35% through the gait cycle

Rearfoot supination causes a

Forefoot pronation