Crural fascia

Last revised by Daniel J Bell on 10 Jul 2022

The crural fascia or deep fascia of the lower leg is a thick connective tissue fascia that invests the muscles of the lower leg and divides them into the four compartments of the lower leg 1,2:

The crural fascia envelopes the lower leg from the knee to the ankle with coverage of the popliteal fossa posteriorly. It is superiorly continuous with the fascia lata of the thigh as well as several expansions of the femoral muscles and inferiorly with the dorsalis pedis facia.

It forms the following intermuscular septa and thus the compartments of the lower leg:

  • anterior intermuscular septum
  • posterior intermuscular septum
  • transverse intermuscular septum

The anterior and posterior septa are attached to the anterior and posterior margins of the fibula. The transverse intermuscular connects the posterior margin of the fibula to the posteromedial margin of the tibia 1,2. It is superiorly attached to several structures including the popliteus fascia, expansions of the semimembranosus and biceps femoris tendons, and inferiorly continuous with the flexor retinaculum and the superficial peroneal retinaculum. Posteroinferiorly it also fuses with the Achilles paratenon.

The crural fascia forms different compartments separating muscle groups with distinctive embryological origin, function, blood supply and innervation 4. It also seems to transmit muscular forces over different segments of the limb 5. Another function is the circulatory-supporting role together with the valves of veins and lymphatics in ensuring that blood and lymph are flowing when muscles contract against the fascia 6.

Musculotendinous attachments of the crural fascia include the following:

Ligamentous or bony attachments of the crural fascia are:

The crural fascia of the leg borders and is continuous with the following structures 1,2:

A virtually uninterrupted plane of sliding exists between the crural fascia and the gastrocnemius muscle 6.

The crural fascia receives blood from the inferior medial and lateral genicular artery, circumflex fibular artery and branches of the anterior, posterior tibial and fibular arteries.

The crural fascia is innervated by the nerves supplying the muscles they invest 4

The crural fascia consists of three layers of parallel collagen fiber bundles with a thickness of up to 0.3 mm each and only a few elastic fibers divided by thin layers of loose connective tissue 5,6.

On ultrasound, the crural fascia appears as a thick hyperechoic lamina of connective tissue which can be distinguished from the epimysia of the adjacent muscles by interposed layers of hypoechoic connective tissue 4.

It can also show thickening and fluid within the fascia in the setting of injury 7,8.

MRI can be used to depict the crural fascia especially in the setting of pathological conditions.

The crural fascia or deep fascia of the lower leg is related to the following pathologies 7,9:

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