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Canals and Fossae of the Lower Limb

For medical students2 min readUpdated 2026-10-10

The canals and fossae of the lower limb are topographic and anatomical spaces through which major neurovascular bundles pass. Knowledge of their boundaries and contents is essential for understanding infection pathways, hernia formation, and surgical approaches.

Femoral canalDoes not exist normally; forms only during femoral herniation
Adductor canalTransmits femoral vessels into the popliteal fossa
Popliteal fossaDiamond-shaped, contains popliteal vessels and nerves
Crurumpopliteal canalRuns between the layers of the posterior leg muscle group

Femoral Canal (*canalis femoralis*)

This space is pathological and forms exclusively during the development of a femoral hernia, when internal organs protrude inferior to the inguinal ligament into the vascular lacuna. The canal is located lateral to the muscular lacuna and is bounded anteriorly and superiorly by the inguinal ligament (lig. inguinale) and the transversalis fascia, posteriorly and medially by the pectineal ligament (lig. pectineale), and anteriorly and inferiorly by the femoral vein.

The canal has two openings:

Inside the canal are loose connective tissue, lymphatic vessels, and deep inguinal lymph nodes (including Cloquet's node). In pathology, the hernial sac passes through here.

Adductor Canal (*canalis adductorius*, Hunter's canal)

Located in the middle and lower thirds of the thigh in the anteromedial region, between the adductor muscles. The canal begins in the upper third of the thigh, where the intermuscular septum overhangs the space, and ends at the adductor hiatus (hiatus tendineus/adductorius), leading into the popliteal fossa.

Walled by:

The femoral artery (a. femoralis), which then becomes the popliteal artery, the femoral vein (v. femoralis), and the saphenous nerve (n. saphenus) pass through the canal. The saphenous nerve does not enter the adductor hiatus; instead, it exits the canal through the anterior opening together with the descending genicular artery.

Popliteal Fossa (*fossa poplitea*)

Diamond-shaped and located on the posterior aspect of the knee joint.

Boundaries:

The floor of the fossa is formed by the joint capsule of the knee, the oblique popliteal ligament (lig. popliteum obliquum), and the posterior surface of the femur. The roof is formed by skin and fascia.

Contents are arranged in layers from superficial to deep: the tibial nerve (n. tibialis) lies most superficially, the popliteal vein (v. poplitea) lies deeper, and the popliteal artery (a. poplitea) lies deepest on the floor. The common fibular nerve (n. fibularis communis) runs laterally.

Crurumpopliteal Canal (*canalis cruropopliteus*, posterior compartment canal)

Runs from the popliteal fossa inferiorly, situated between the superficial muscles of the leg (triceps surae, m. triceps surae) and its deep layer (tibialis posterior, flexor digitorum longus, and flexor hallucis longus).

Proximally, the canal is closed by fascia, and distally it opens near the medial malleolus. It transmits the posterior tibial artery (a. tibialis posterior), accompanying veins, and the tibial nerve (n. tibialis). Compression of structures within this canal can lead to pseudo-claudication syndrome.

Frequently asked questions

Where is the external ring of the femoral canal located and what forms it?

The external ring of the femoral canal is located in the fascia lata 1–2 cm inferior to the medial third of the inguinal ligament. It is represented by the saphenous opening (hiatus saphenus), covered by the cribriform fascia (fascia cribrosa).

The opening is formed by the following structures:

  • Sickle-shaped margin (margo falciformis) — bounds the opening laterally.
  • Superior horn (cornu superius) — upper part of the margin.
  • Inferior horn (cornu inferius) — lower part of the margin.
What forms the anterior and posterior walls of the crurumpopliteal canal?

The anterior and posterior walls of the crurumpopliteal canal are formed by the muscles of the deep and superficial layers of the posterior leg region.

The walls are formed by:

  • Anterior wall — formed by the tibialis posterior muscle (m. tibialis posterior), and inferiorly by the flexor digitorum longus muscle (m. flexor digitorum longus).
  • Posterior wall — formed by the soleus muscle (m. soleus).
What openings does the crurumpopliteal canal have?

The crurumpopliteal canal has three main openings: one inlet and two outlets.

  • Inlet — bounded anteriorly by the popliteus muscle (m. popliteus) and posteriorly by the tendinous arch of the soleus muscle (arcus tendineus m. solei).
  • Upper outlet — bounded laterally by the neck of the fibula (collum fibulae), superiorly by the popliteus muscle (m. popliteus), and inferomedially by the origin of the tibialis posterior muscle (m. tibialis posterior).
  • Lower outlet — located at the medial margin of the soleus muscle (m. soleus), medial to the calcaneal tendon.
Which musculofibular canals branch off from the crurumpopliteal canal?

The inferior musculofibular canal (canalis musculoperoneus inferior) is associated with the crurumpopliteal canal.

  • Inferior musculofibular canal is formed by the fibula and the flexor hallucis longus muscle (m. flexor hallucis longus).
  • Its contents are the fibular artery and veins (a. et vv. fibulares).
  • The fibular artery branches off the posterior tibial artery and runs laterally into the inferior musculofibular canal.
Where is the internal ring of the femoral canal located and how is it formed?

The femoral ring (anulus femoralis) is located in the vascular lacuna. It is bounded anteriorly by the inguinal ligament, posteriorly by the pectineal ligament, medially by the lacunar ligament, and laterally by the femoral vein.

What structures pass through the adductor canal?

The femoral artery, femoral vein, and saphenous nerve (n. saphenus) pass through it. The artery and vein enter the popliteal fossa, while the nerve exits through the anterior wall of the canal.

How are the neurovascular bundle elements arranged in the popliteal fossa?

From superficial to deep (and from medial to lateral), the order is: tibial nerve (n. tibialis), popliteal vein (v. poplitea), and popliteal artery (a. poplitea).

Go deeper

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