Boundaries and external landmarks of the ankle region
The ankle region is bounded by two planes: the upper plane runs horizontally through the bases of both malleoli, and the lower plane runs at the level of their apices.
Bony and soft-tissue landmarks that are easily identifiable upon inspection:
- At the sides project the medial and lateral malleoli.
- Between the malleoli anteriorly lie the tendons of the extensor muscles. They are outlined particularly well when the patient performs dorsiflexion of the foot.
- To the sides of the tendons lie the premalleolar sulci.
Clinical significance: the contour of the premalleolar sulci is an important diagnostic sign. If inflammatory effusion or blood accumulates in the ankle joint cavity, these sulci smooth out and transform into bulging premalleolar eminences.
Superficial layers and neurovascular structures
The skin in the ankle region is thin and mobile, and the subcutaneous adipose tissue is poorly developed. Important structures run within the superficial fascia layer, the topography of which depends on the side of the joint.
Medial side (anterior to the medial malleolus): Here, the great saphenous vein (v. saphena magna) and the saphenous nerve (n. saphenus) are located within the superficial fascia. Practical significance: due to the consistency of the anatomical position of the great saphenous vein, surgeons most frequently perform venesection (exposure of the vessel) at this point for the placement of an infusion catheter.
Lateral side (anterior to the lateral malleolus): In this section, the superficial fascia layer contains branches of the superficial fibular nerve (n. fibularis superficialis).
Lateral retromalleolar region
The retromalleolar regions are bounded vertically by the same planes as the anterior part of the ankle. Anteriorly, the lateral region is bounded by a vertical line drawn through the greatest convexity of the lateral malleolus, and posteriorly by the lateral margin of the calcaneal (Achilles) tendon.
In this zone, beneath the superior and inferior fibular retinacula (retinaculum mm. fibularium superius et inferius), run the tendons of the long and short fibular muscles. They are enclosed in a common synovial sheath (vag. synovialis mm. fibularium communis).
Also within the region and adjacent areas of the foot are:
- Calcaneal tendon (tendo calcanei).
- Inferior extensor retinaculum (retinaculum mm. extensorum inferius).
- Synovial sheaths and tendons of the long extensors of the toes and the hallux.
- Short extensor of the toes (m. extensor digitorum brevis) and abductor digiti minimi muscle (m. abductor digiti minimi).
- Calcaneal branches of the fibular artery (rami calcanei a. fibularis).
Medial retromalleolar region
Anteriorly, this region is bounded by a line through the medial malleolus, and posteriorly by the medial margin of the calcaneal tendon. Beneath the skin here also run the v. saphena magna and n. saphenus.
Beneath the flexor retinaculum (retinaculum mm. flexorum) within their own synovial sheaths run the tendons of the deep muscles of the leg:
- Tibialis posterior muscle (m. tibialis posterior).
- Flexor digitorum longus muscle (m. flexor digitorum longus).
- Flexor hallucis longus muscle (m. flexor hallucis longus).
Topography of the neurovascular bundle Here runs the tibial bundle (posterior tibial artery and tibial nerve), which gives off calcaneal branches (rr. calcanei). An important division occurs in this same area: the vessels and nerve branch into the medial and lateral plantar arteries and nerves (a. et n. plantaris medialis et lateralis). The resulting bundles head into the calcaneal canal (canalis calcaneus) and proceed further onto the sole.
Ligamentous apparatus of the ankle joint
The stability of the joint (articulatio talocruralis) and neighboring joints (e.g., the talonavicular joint) is ensured by a complex of strong ligaments. In a frontal section, the following key structures can be distinguished:
- Medial group: deltoid ligament (lig. deltoideum), which includes the tibionavicular ligament (lig. tibionaviculare).
- Anterior group: anterior talotibial ligament (lig. talotibiale anterius).
- Lateral and posterior groups: posterior talofibular ligament (lig. talofibulare posterius).
- Deep ligaments of the foot: bifurcated ligament (lig. bifurcatum) and interosseous talocalcaneal ligament (lig. talocalcaneum interosseum).
Briefly: answers to topical questions
Which ligaments make up the lateral complex of the ankle joint?
The lateral ligaments of the ankle joint include:
- Anterior talofibular ligament (lig. talofibulare anterius).
- Posterior talofibular ligament (lig. talofibulare posterius).
- Calcaneofibular ligament (lig. calcaneofibulare).
In what order from anterior to posterior are the tendons and neurovascular bundle elements arranged posterior to the medial malleolus?
Posterior to the medial malleolus in the malleolar canal, the structures are arranged from anterior to posterior in the following order:
- Tendon of the tibialis posterior (m. tibialis posterior) — occupies the most anterior position.
- Tendon of the flexor digitorum longus (m. flexor digitorum longus).
- Posterior tibial artery and veins (a. tibialis posterior et vv. tibiales posteriores).
- Tibial nerve (n. tibialis).
- Tendon of the flexor hallucis longus (m. flexor hallucis longus) — occupies the most posterior and deep position.
Which nerves provide sensory innervation to the skin in the ankle joint region?
Sensory innervation of the skin in the ankle joint region is provided by branches of two nerves running in the subcutaneous tissue.
- Saphenous nerve (n. saphenus) — located on the medial side, along the anterior surface of the medial malleolus, accompanying the great saphenous vein.
- Superficial fibular nerve (n. fibularis superficialis / n. peroneus superficialis) — its branches run in the superficial fascia layer on the lateral side, anterior to the lateral malleolus.
Which bones form the ankle joint?
The ankle joint is formed by three bones: the tibia, fibula, and talus.
- Tibia (tibia) — participates with its inferior articular surface and the articular surface of the medial malleolus.
- Fibula (fibula) — participates with the articular surface of the lateral malleolus.
- Talus (talus) — participates with the trochlea of the talus (trochlea tali).
The articular surfaces of the lower ends of both leg bones embrace the trochlea of the talus, forming a joint that resembles a fork in shape.
Class and exam questions
How to visually determine the presence of effusion in the ankle joint?
Normally, premalleolar sulci are visible on the sides of the extensor tendons. When effusion accumulates in the joint, they smooth out and transform into premalleolar eminences.
Why is venipuncture most frequently performed in the ankle region?
Anterior to the medial malleolus, the great saphenous vein (v. saphena magna) has a very consistent anatomical position and lies superficially, making it an ideal target for exposure and catheterization.
Where do the tibial vessels and nerves go from the retromalleolar region?
The tibial artery and nerve divide into medial and lateral plantar branches, which enter the calcaneal canal (canalis calcaneus) and continue onto the plantar surface of the foot.
What else to study on this topic
- Structure and topography of the tarsal tunnel (canalis calcaneus)
- Topography of the synovial sheaths of the foot extensor muscles
- Retinacula of the ankle region (retinaculum mm. flexorum, extensorum, fibularium)
- Branching of the fibular artery and its calcaneal branches
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