Medial and Lateral Malleoli

The medial and lateral malleoli are prominent bony landmarks on either side of the ankle. The medial malleolus is formed by the distal end of the tibia, while the lateral malleolus is formed by the distal end of the fibula. Together, they form the medial and lateral boundaries of the ankle mortise and can be readily identified by inspection and palpation.^[1][2]

The two malleoli are not symmetrical. The lateral malleolus extends farther distally and lies somewhat more posteriorly than the medial malleolus. Their different positions influence the stability and permitted movements of the talocrural joint.

Because both malleoli are subcutaneous and easily palpable, they are important landmarks during physical examination, assessment of ankle injuries, localization of tendons and neurovascular structures, interpretation of imaging, and surgical approaches to the ankle.

Location

The malleoli are located at the distal ends of the bones of the leg, immediately proximal to the foot.

The medial malleolus projects from the medial side of the distal tibia. The lateral malleolus projects from the distal fibula on the lateral side of the ankle.

They flank the talus and form the easily recognizable bony prominences on either side of the ankle.

General Anatomy

Feature	Medial Malleolus	Lateral Malleolus
Bone	Tibia	Fibula
Position	Medial ankle	Lateral ankle
Relative level	More proximal	Extends farther distally
Relative position	More anterior	More posterior
Major ligament association	Deltoid ligament	Lateral ligament complex
Articulation	Talus	Talus
Surface accessibility	Subcutaneous and palpable	Subcutaneous and palpable

Medial Malleolus

The medial malleolus is a downward projection from the medial side of the distal tibia. It forms the prominent bony landmark on the medial side of the ankle.^[1][3]

Its lateral articular surface articulates with the medial surface of the talus. The malleolus also provides attachment for the strong medial ligament complex of the ankle.

The medial malleolus is relatively broad and blunt compared with the more elongated lateral malleolus.

Lateral Malleolus

The lateral malleolus is formed by the distal end of the fibula.

It extends farther inferiorly than the medial malleolus and is positioned somewhat posterior to it. Its medial surface contains an articular facet for the lateral surface of the talus.

The lateral malleolus provides attachment for the principal lateral ligaments of the ankle and serves as a pulley around which the fibularis tendons pass.

Relative Position of the Malleoli

The medial and lateral malleoli occupy different levels and planes.

The lateral malleolus is located more distally and more posteriorly than the medial malleolus. This relationship can be appreciated by palpating both landmarks simultaneously.

The asymmetry is functionally important because it contributes to the configuration of the ankle mortise and limits excessive side-to-side movement of the talus.

Ankle Mortise

The distal tibia and fibula form a socket known as the ankle mortise, which receives the trochlea of the talus.

The roof of the mortise is formed by the inferior articular surface of the tibia. The medial malleolus forms its medial wall, while the lateral malleolus forms its lateral wall.

This arrangement provides substantial bony stability while allowing dorsiflexion and plantarflexion at the talocrural joint.

Relationship to the Talus

Both malleoli articulate with the talus.

The medial malleolus articulates with the medial surface of the talus, while the lateral malleolus articulates with its lateral surface.

The trochlea of the talus is wider anteriorly than posteriorly. During dorsiflexion, the wider anterior portion enters the ankle mortise, increasing the stability of the joint.

Palpation of the Medial Malleolus

The medial malleolus is easily palpated on the medial side of the ankle.

Its anterior border, tip, and posterior border can usually be followed through the skin. Because it is largely subcutaneous, little muscular tissue obscures the landmark.

Palpation of the medial malleolus provides a reference point for locating the deltoid ligament, posterior tibial artery, tibial nerve, and several tendons passing behind the medial ankle.

Palpation of the Lateral Malleolus

The lateral malleolus can be readily palpated at the distal end of the fibula.

Its tip lies inferior to the tip of the medial malleolus. The anterior and posterior borders can also be followed proximally into the distal fibula.

The landmark is particularly important when examining the lateral ankle ligaments and fibularis tendons.

Structures Anterior to the Medial Malleolus

The great saphenous vein passes anterior to the medial malleolus as it ascends from the medial side of the foot into the leg.

The saphenous nerve accompanies the vein in this general region and supplies cutaneous sensation along the medial ankle and foot.

The medial malleolus therefore provides an important surface landmark for identifying these superficial structures.

Structures Posterior to the Medial Malleolus

Several important tendons and neurovascular structures pass behind the medial malleolus beneath the flexor retinaculum.

From anterior to posterior, the major structures are:

• Tibialis posterior tendon
• Flexor digitorum longus tendon
• Posterior tibial artery and accompanying veins
• Tibial nerve
• Flexor hallucis longus tendon

These structures occupy the region known as the tarsal tunnel.

Tarsal Tunnel

The tarsal tunnel lies posterior and inferior to the medial malleolus.

Its roof is formed by the flexor retinaculum, while the underlying bones and associated structures form its floor.

The medial malleolus is therefore one of the principal palpable landmarks used to identify the location of the tarsal tunnel and the tibial neurovascular bundle.

Posterior Tibial Pulse

The posterior tibial artery can be palpated posterior and slightly inferior to the medial malleolus.

The pulse is generally sought in the interval between the medial malleolus and the calcaneal region.

Because the malleolus is easily identified, it provides a reliable bony reference for clinical assessment of the posterior tibial pulse.

Structures Posterior to the Lateral Malleolus

The tendons of fibularis longus and fibularis brevis pass posterior to the lateral malleolus.

They are retained against the fibula by the superior fibular retinaculum before continuing toward the lateral side of the foot.

The lateral malleolus acts as a pulley that changes the direction of pull of these tendons.

Fibularis Tendons

The fibularis brevis tendon generally lies anterior to the fibularis longus tendon as the two pass behind the lateral malleolus.

Fibularis brevis continues toward the tuberosity at the base of the fifth metatarsal, while fibularis longus passes farther distally and then crosses the plantar aspect of the foot.

The tendons may become more apparent during resisted eversion of the foot.

Structures Anterior to the Lateral Malleolus

The region immediately anterior to the lateral malleolus is important because it contains the anterior talofibular ligament, one of the principal ligaments of the lateral ankle.

The ligament extends from the anterior aspect of the lateral malleolus toward the talus.

This area is commonly examined after inversion injuries because the anterior talofibular ligament is frequently injured in lateral ankle sprains.

Deltoid Ligament

The deltoid ligament is the strong medial collateral ligament complex of the ankle and attaches proximally to the medial malleolus.

Its fibers spread from the malleolus toward the talus, calcaneus, and navicular region.

The broad configuration and strength of the deltoid ligament contribute substantially to medial ankle stability and resistance to excessive eversion.

Lateral Ligament Complex

The lateral malleolus provides attachment for the three major components of the lateral ligament complex:

• Anterior talofibular ligament
• Calcaneofibular ligament
• Posterior talofibular ligament

These ligaments stabilize the lateral side of the ankle and restrict excessive inversion, translation, and rotation of the talus.

Anterior Talofibular Ligament

The anterior talofibular ligament extends from the anterior portion of the lateral malleolus to the talus.

It is positioned approximately horizontally when the ankle is in neutral position and becomes particularly vulnerable during plantarflexion combined with inversion.

It is the ligament most commonly injured in a typical lateral ankle sprain.

Calcaneofibular Ligament

The calcaneofibular ligament extends from the lateral malleolus toward the lateral surface of the calcaneus.

It crosses both the ankle and subtalar regions and contributes to lateral stability.

The ligament is positioned more vertically than the anterior talofibular ligament and may be injured in more substantial inversion injuries.

Posterior Talofibular Ligament

The posterior talofibular ligament extends from the posterior aspect of the lateral malleolus toward the posterior talus.

It is generally stronger than the anterior talofibular ligament and is less commonly injured in routine ankle sprains.

Its location places it deep within the posterior aspect of the lateral ankle complex.

Distal Tibiofibular Syndesmosis

The distal tibia and fibula are connected by the distal tibiofibular syndesmosis.

This fibrous articulation stabilizes the relationship between the two bones and maintains the integrity of the ankle mortise.

Its ligamentous components include the anterior inferior tibiofibular ligament, posterior inferior tibiofibular ligament, interosseous ligament, and associated fibers.

Relationship to Ankle Movement

The malleoli help guide and constrain movement of the talus during dorsiflexion and plantarflexion.

During dorsiflexion, the wider anterior portion of the talar trochlea enters the mortise and produces a tightly fitting configuration.

During plantarflexion, the narrower posterior portion occupies the mortise, allowing somewhat greater accessory movement and making the ankle relatively less stable.

Relationship to Inversion and Eversion

The malleoli contribute to the bony restrictions on excessive movement of the foot.

The more distal lateral malleolus limits excessive eversion and helps stabilize the lateral side of the talus. Ligaments attached to both malleoli provide additional resistance to abnormal inversion and eversion.

Most inversion and eversion occur at joints below the talocrural joint, particularly the subtalar and transverse tarsal joints, rather than as pure movements within the ankle mortise.

Comparison of the Malleoli

Feature	Medial Malleolus	Lateral Malleolus
Parent bone	Tibia	Fibula
Relative position	More anterior	More posterior
Inferior extent	Less distal	More distal
Major ligament	Deltoid ligament	Lateral ligament complex
Major posterior structures	Deep flexor tendons, posterior tibial vessels and tibial nerve	Fibularis longus and brevis tendons
Superficial vascular landmark	Great saphenous vein passes anteriorly	Small saphenous vein is associated with the posterolateral ankle region

Clinical Significance

Ankle Fractures

The malleoli are common sites of fracture because they form the bony boundaries of the ankle joint and transmit forces between the leg and foot.

Fractures may involve the medial malleolus, lateral malleolus, posterior portion of the distal tibia, or combinations of these structures.

The pattern of injury provides information about the forces applied to the ankle and possible associated ligamentous damage.

Bimalleolar Fracture

A bimalleolar fracture involves both the medial and lateral malleolar regions.

Because both sides of the ankle mortise are disrupted, these injuries can substantially compromise ankle stability.

Assessment includes evaluation of fracture displacement, talar alignment, syndesmotic integrity, and associated soft-tissue injury.

Trimalleolar Fracture

A trimalleolar fracture typically involves the medial malleolus, lateral malleolus, and posterior malleolar portion of the distal tibia.

These injuries can affect the congruity and stability of the ankle joint and may involve significant displacement of the talus.

CT may be used to characterize complex fracture anatomy and the size and configuration of posterior malleolar fragments.

Lateral Ankle Sprain

The lateral malleolus is an important landmark during assessment of a lateral ankle sprain.

Inversion injuries commonly affect the anterior talofibular ligament first, with the calcaneofibular ligament potentially involved in more severe injuries.

Tenderness can be localized relative to the lateral malleolus to help distinguish ligamentous injury from possible fracture.

Medial Ankle Sprain

Forceful eversion or rotational trauma can injure the deltoid ligament attached to the medial malleolus.

Because the deltoid ligament is strong, substantial forces may also produce associated fractures or syndesmotic injury.

Medial malleolar tenderness therefore requires consideration of both ligamentous and bony injury.

Syndesmotic Injury

Injury to the distal tibiofibular syndesmosis is commonly referred to as a high ankle sprain.

Disruption of the syndesmotic ligaments can allow abnormal separation or rotation between the distal tibia and fibula and compromise the ankle mortise.

Assessment of the relationship between the malleoli and talus is important when determining ankle stability.

Ottawa Ankle Rules

The posterior borders and tips of the malleoli are important landmarks in the Ottawa Ankle Rules, a clinical decision tool used to help determine when ankle radiographs are indicated after acute injury.

Localized bony tenderness around specified portions of the medial or lateral malleolus, together with assessment of weight-bearing ability, contributes to the decision process.

The rules emphasize accurate palpation of the malleolar bony landmarks rather than generalized tenderness around the ankle.

Tarsal Tunnel Syndrome

The medial malleolus is a key landmark for the tarsal tunnel, where the tibial nerve passes beneath the flexor retinaculum.

Compression or irritation of the tibial nerve in this region can produce sensory symptoms involving the plantar foot and, depending on the level and branches affected, motor abnormalities in intrinsic foot muscles.

Clinical examination of the tunnel is performed in relation to the medial malleolus.

Posterior Tibial Tendon Dysfunction

The tibialis posterior tendon passes immediately behind the medial malleolus before continuing toward the navicular and plantar midfoot.

Pain or swelling along this course can occur with posterior tibial tendon pathology.

The medial malleolus therefore provides a useful landmark for tracing the tendon during physical examination and imaging.

Fibularis Tendon Injury

The fibularis longus and brevis tendons pass behind the lateral malleolus and can be affected by tendinopathy, tearing, instability, or dislocation.

Symptoms are often localized to the posterolateral ankle, where the tendons can be examined relative to the lateral malleolus.

Ultrasound is particularly useful for dynamic evaluation of tendon movement in this region.

Imaging

Radiographs are commonly used to assess the malleoli after ankle trauma and can demonstrate fractures, displacement, mortise alignment, and associated bony abnormalities.

CT provides more detailed evaluation of complex fracture patterns, while MRI can assess associated ligamentous, tendinous, osteochondral, and other soft-tissue injuries.

Ultrasound can dynamically evaluate superficial ligaments and tendons around the malleoli.

Surface Anatomy

The medial and lateral malleoli are among the most prominent and reliable surface landmarks of the lower limb. Both can usually be identified visually and palpated directly beneath the skin.

The medial malleolus is broad and lies slightly more anteriorly. The lateral malleolus is more elongated, positioned farther posteriorly, and extends farther distally.

These landmarks provide reference points for locating the ankle joint line, ligament attachments, tendons, superficial veins, posterior tibial neurovascular structures, tarsal tunnel, and fibularis tendons. Their accessibility also makes them fundamental landmarks during examination of ankle trauma and interpretation of ankle alignment.