Overview of the pelvis and lower limb

Iliac fascia

The thin iliac fascia covers psoas and iliacus. The external iliac vessels are anterior to the fascia but the branches of the lumbar plexus are posterior to it. Lateral to the femoral vessels, the iliac fascia is continuous with the posterior margin of the inguinal ligament and the transversalis fascia. Medially, it passes behind the femoral vessels to become the pectineal ligament, attached to the pecten pubis. At the junction between its lateral and medial parts it is attached to the iliopubic ramus and the capsule of the hip joint. It thus forms a septum between the inguinal ligament and the hip bone, dividing the space here into a lateral part – the muscular space – which contains psoas major and iliacus and the femoral nerve, and a medial part – the vascular space – which transmits the femoral vessels. The iliac fascia continues downwards to form the posterior wall of the femoral sheath.

Obturator membrane

The obturator membrane is a thin aponeurosis that closes most of the obturator foramen, leaving a superolateral aperture, the obturator canal, through which the obturator vessels and nerve leave the pelvis and enter the thigh. The outer and inner surfaces of the obturator membrane provide attachments for obturator externus and internus, respectively. Some fibres of the pubofemoral ligament of the hip joint are attached to its outer surface.

Fascia lata

The fascia lata, the wide fascia musculorum of the thigh, is thicker in the proximal and lateral parts of the thigh, where tensor fasciae latae and an expansion from gluteus maximus are attached to it. It is attached superiorly and posteriorly to the back of the sacrum and coccyx, laterally to the outer margin of the iliac crest, anteriorly to the inguinal ligament and superior ramus of the pubis, and medially to the inferior ramus of the pubis, the ramus and tuberosity of the ischium, and the lower border of the sacrotuberous ligament. From the iliac crest it descends as a dense layer over gluteus medius to the upper border of gluteus maximus, where it splits into two layers, one passing superficial and the other deep to the muscle. These layers reunite at the lower border of the muscle.

Iliotibial tract

Over the lateral surface of the thigh, the fascia lata thickens to form a strong band, the iliotibial tract, the superior end of which splits into two layers. These enclose and anchor tensor fasciae latae and receive, posteriorly, most of the tendon of gluteus maximus. The superficial layer ascends lateral to tensor fasciae latae to the iliac crest; the deeper layer passes upwards and medially, deep to the muscle, and blends with the lateral part of the hip joint capsule. Distally, the iliotibial tract is attached via its tubercle (Gerdy's tubercle) to the anterolateral aspect of the lateral condyle of the tibia.

Intermuscular septa

The deep surface of the fascia lata yields two intermuscular septa, which are attached to the whole of the linea aspera and to its proximal and distal prolongations. The lateral septum extends from the attachment of gluteus maximus to the lateral femoral condyle; it lies between vastus lateralis anteriorly and the short head of biceps femoris posteriorly, and provides a partial attachment for them. The medial septum lies between vastus medialis and the adductors and pectineus. Numerous smaller septa, such as that separating the thigh adductors and flexors, pass between the individual muscles, ensheathing them and sometimes providing partial attachments for their fibres.

Tela subcutanea and fascia musculorum

The more superficial fascia of the lower limb (tela subcutanea) becomes thinner peripherally. In the thigh, as elsewhere in the limbs, it is made of loose areolar tissue containing fat. It participates in the integrity of the skin and provides support for subcutaneous structures such as cutaneous nerves and superficial veins. It prevents the superficial veins from being displaced during limb movement by virtue of its connections to their adventitia.

The deeper fascia of the lower limb (fascia musculorum) is a well-defined aponeurotic fascia that constrains the musculature. Septa pass from its deep surface to the bones within, confining the functional muscle groups within osteofascial compartments. It is sufficiently tough to provide additional areas of muscle attachment and ensure maximal function. Elsewhere, thickenings in the fascial skeleton form the fibrous retinacula, where tendons cross joints. This pattern of soft tissue organization has a bearing on the physiological effects of the muscles and is crucial for efficient venous return from the limb. The fascial planes also control and direct the spread of pathological fluids within the limb and are important determinants of the degree and direction of displacement seen in long-bone fractures.

The fascia musculorum of the leg (crural fascia) is continuous with the fascia lata. Below, it is continuous with the extensor and flexor retinacula. Laterally, it is continuous with the anterior and posterior crural intermuscular septa, which are attached to the anterior and posterior borders of the fibula, respectively. A broad sheet of fascia, the transverse intermuscular septum (deep transverse fascia) of the leg, passes between the superficial and deep parts of the posterior compartment of the leg.

The plantar aponeurosis on the sole of the foot consists of densely compacted collagen fibres orientated longitudinally and transversely. It runs anteriorly from the calcaneus, and at the heads of the metatarsals it divides into five bands, one extending out to each digit.