The basis of any surgical discipline and radiological imaging is structural anatomy. This article envisages clarifying the basics of lower limb anatomy with focus on the gluteal region, posterior thigh and the popliteal fossa. The muscles of the gluteal region are specialized to bear weight and maintain the horizontal balance of the pelvis. The posterior thigh muscles are the lateral rotators of the hip and the popliteal fossa is responsible mainly for extension/flexion and adduction.

jogging-lower-limb-anatomy

Image: “Jogging” by komposita. License: CC0 1.0


Introduction to Lower Limb Anatomy

The anatomical lower limb is inclusive of the foot, leg, thigh and the gluteal region. Human lower limb is specially adapted to bear weight in upright position and to walk. The gluteal muscles, extensors of the knee and the posterior calf muscles are mainly involved and, hence, specialized to suit these needs.

Gluteal Region

The posterolateral surface of the buttocks constitutes the gluteal region. The muscles of the gluteal region, namely, the glutei maximus, medius and minimus, form the bulk of the buttock. Posterior to the bony pelvis, the mass of muscles in the gluteal region is limited by the inferior gluteal cleft inferiorly and the intergluteal cleft medially.

There are 2 layers of muscles in the gluteal region:

  • Superficial — Gluteal muscles and tensor fasciae latae
  • Deep — Lateral rotators and hip stabilizers

The gluteus medius and minimus are fan-shaped and are positioned deep to the gluteus maximus. Laterally, the tensor fasciae latae helps to stabilize the lateral aspect of the knee joint.

The anatomical and functional details of these muscles can be tabulated as follows:

Muscle Origin Insertion Nerve supply Function
Gluteus maximus Ilium posterior to posterior gluteal line, posterior sacrum and coccyx and sacrotuberous ligament. Iliotibial tract (75 %) and gluteal tuberosity (25 %) Inferior gluteal nerve( S1, S2) Extends hip and assists lateral rotation
Gluteus medius External ilium between anterior and inferior gluteal lines Greater trochanter of femur Superior gluteal nerve (L4, L5, S1) It brings about abduction and medial rotation of the pelvis. It keeps the pelvic level when opposite limb is off ground.
Gluteus minimus External ilium between anterior and inferior gluteal lines Greater trochanter of femur Superior gluteal nerve (L4, L5, S1) Same as gluteus medius; it abducts and medially rotates the pelvis. It keeps the pelvic level when opposite limb is off ground
Tensor fasciae latae Anterior superior iliac spine Iliotibial tract to lateral condyle of tibia. Superior gluteal nerve (L4, L5, S1) This muscle assists in flexing the hip and stabilizing the knee joint.

Neurovasculature of Lower Limb Anatomy

The femoral artery

The majority of the lower limb is supplied by the femoral artery. The femoral artery is the direct continuation of the external iliac, as it passes deep to the inguinal ligament through the retro-inguinal space. The femoral artery enters the femoral triangle deep to inguinal ligament.

It exits canal via the adductor hiatus to enter popliteal fossa and becomes the popliteal artery.

Within the femoral triangle, the femoral artery gives profunda brachii artery which is a deep artery. It passes deep to adductor longus and supplies thigh musculature.

The femoral artery gives rise to lateral and medial circumflex arteries. It courses around the proximal femur. The medial circumflex artery passes deep to iliopsoas and pectineus. The lateral circumflex artery goes across the joint capsule anterior to quadrates femoris.

Thigh arteries schema-lower limb anatomy

Image: “Thigh arteries schema” by Jecowa. License: CC BY 3.0

Exception 1

Gluteal region is supplied by gluteal arteries (internal iliac artery) – important anastomoses may occur between the two.

Exception 2

Medial thigh is supplied by the obturator artery (internal iliac artery). As the femoral passes distally, it changes its name to reflect its new location.

As the femoral artery descends through the thigh; perforating arteries course around the femur to supply adductor magnus and posterior compartment.

Gluteal arteries

There are 2 gluteal arteries, namely, the superior and inferior gluteal artery, respectively.

Internal-iliac-branches-lower limb anatomy

Image: “The arteries of the pelvis. Right side (distal from spectator).” by Mikael Häggström. License: Public Domain

They arise from the internal iliac artery within the pelvis. While the superior gluteal artery enters the gluteal region by passing through the suprapiriform (above piriformis) foramen, the inferior gluteal artery passes through the infrapiriform foramen.

  1. The superior gluteal artery supplies gluteus medius, minimus and tensor fascia lata muscles.
  2. The inferior gluteal artery supplies the gluteus maximus, obturator internus, quadrates femoris and proximal posterior thigh muscles.

An important connection exists between the profunda brachii and inferior gluteal arteries; known as the “Cruciate anastomosis”. The contributing branches within the same can be mentioned as follows:

  • Inferior gluteal: descending branch
  • Medial circumflex: transverse branch
  • Lateral circumflex: transverse branch
  • First perforating artery: ascending branch
The piriformis muscle is an important landmark for neurovasculature relations in the gluteal region.

The important structures and their relative location to the piriformis muscle can be summarized as follows:

  1. Superior — Superior gluteal artery, vein and nerve
  2. Inferior — Inferior gluteal artery, vein and nerve
  3. Inferior — Sciatic and posterior cutaneous nerve of thigh
  4. Inferior — Pudendal neurovascular bundle (then enters perineum via lesser sciatic foramen)

Posterior Thigh

The majority of muscles in the thigh act on the hip and knee joint. There are two types of movements possible, namely, flexion/extension and adduction. Abduction is performed by muscles in the gluteal region. The posterior thigh muscles bring about lateral rotation, extension of the hip and flexion of the knee joint.

Posterior Thigh Muscles

Piriformis, gemelli, obturator internus and quadrates femoris are the lateral rotators of the hip. Basic details about these posterior thigh small muscles can be summarized as follows:

Muscle Origin Insertion Nerve supply Function
Piriformis Anterior surface of sacrum Greater trochanter (superior surface) Anterior rami of S1 Lateral rotation of extended hip and abduction of flexed hip
Gemelli Superior: Ischial spine

Inferior: Ischial tuberosity

Greater trochanter (medial surface) Nerve to obturator internus (S1)

Nerve to quadrates femoris (L5, S1)

Nerve to

Obturator internus (S1)

Obturator internus Pelvic surface of ilium and ischium, and obturator membrane
Quadratus femoris Ischial tuberosity Intertrochanteric crest Nerve to quadrates femoris (L5, S1) Lateral rotation, and holds head of femur in acetabulum.
Hamstring tear lower limb anatomy

Image: “Tear of the hamstrings muscles at the ischial tuberosity seen on MRI (coronal STIR). The arrowheads indicate the tuber and the retracted tendon stump. Significant bleeding around and into the muscles.” by Hellerhoff. License: CC BY-SA 3.0

Posterior to the femur within the thigh are the ‘Hamstrings’ muscles. The Semimembranous, semitendinosus and long head of biceps femoris constitute the hamstrings. They originate from ischial tuberosity and insert onto tibia and fibula, thus, cross two joints: hip and knee.

The short head of biceps is not a hamstring, as it crosses only the knee joint and is innervated via the common fibular nerve.

They are supplied by perforating branches which originate from profunda femoris (branch of femoral artery). These pierce adductor magnus to enter the posterior compartment.

The anatomical nature and functional status of the muscles of the posterior thigh “hamstrings” can be summarized as follows:

Muscle Origin Insertion Nerve supply Function
Biceps femoris Long head: Ischial tuberosity

Short head: Linea aspera and lateral supracondylar line

Lateral surface of fibula Long head: Tibial division of sciatic nerve (L5, S1)

Short head: Common fibular division of sciatic nerve (S1)

Flexes knee joint and lateral rotation when flexed

Extends hip joint

Semitendinosus Ischial tuberosity Medial surface of proximal tibia Tibial division of sciatic nerve (L5,S1) Extends hip joint
Semimembranosus Ischial tuberosity Posterior surface of medial condyle of tibia Tibial division of sciatic nerve (L5,S1) Flex knee joint and medial rotation when flexed

Cross-section of the thigh

The transverse section of the thigh reveals the fascia lata forming three muscular compartments. The septae in between these compartments can be mentioned as follows:

  1. Lateral — femoral intermuscular septum
  2. Medial — femoral intermuscular septum
  3. Posterior — femoral intermuscular septum

The 3 compartments thus formed are anterior, posterior and medial thigh compartment.

thigh-cross-section-lower-limb-anatomy

Image: “Thigh cross section” by Mcstrother. License: CC BY 3.0

The nerve supply of each compartment can be mentioned as follows:

  1. Anterior (extensor compartment) — Femoral nerve
  2. Posterior (flexor compartment) — Tibial nerve
  3. Medial (adductor compartment) — Obturator nerve

Arterial supply of the Lower Limbs

3 or 4 perforating arteries from profunda brachii pierce adductor magnus to enter the posterior compartment of thigh. They typically send superior and inferior branches to join with adjacent perforating arteries. Superiorly, inferior gluteal artery and inferiorly, the popliteal artery connect to them. They give branches to the sciatic nerve.

Popliteal Fossa

Popliteal fossa is a fat-filled, diamond-shaped space located posterior to the knee joint. It contains all the neurovascular structures that pass from the thigh to the leg.

The boundaries of the popliteal fossa can be tabulated as follows:

Boundary Structure at the boundary
Superolaterally Biceps femoris
Superomedially Semimembranosus
Inferolaterally Lateral head of gastrocnemius
Inferomedially Medial head of gastrocnemius
Roof Popliteal fascia and skin
Floor Popliteal surface of femur and popliteus fascia and muscle

Popliteal fossa: contents

All neurovascular structures that pass from the thigh to the leg are basically the contents of the popliteal fossa.

popliteal-fossa-lower-limb-anatomy

Image: “Lymph glands of popliteal fossa” by Henry Vandyke Carter. License: Public Domain

The same can be mentioned as follows for easy memorization

  • Small saphenous vein entering popliteal vein
  • Popliteal artery and associated branches
  • Tibial and common fibular nerves
  • Posterior cutaneous nerve of the thigh
  • Popliteal lymph nodes
  • Fat

Popliteal artery

Popliteal-artery-lower-limb-anatomy

Image: “Popliteal artery” by Mikael Häggström. License: Public Domain

Popliteal artery is the direct continuation of the femoral artery within the popliteal fossa. It terminates by dividing into anterior and posterior tibial arteries at the inferior border of popliteus.

The popliteal artery gives rise to the 5 genicular arteries that supply the joint capsule and ligaments of knee joint. They form the genicular anastomosis. They also receive descending branches from femoral and lateral circumflex arteries. They can be summarized as follows:

  • Superior lateral
  • Superior medial
  • Inferior lateral
  • Inferior medial
  • Middle

Summary of Lower Limb Anatomy

The gluteal region

The gluteal region consists of the glutei maximus, medius and minimus and tensor fasciae latae muscles. They are specialized to bear weight and maintain the horizontal balance of the pelvis while one leg goes in swing phase during walking. The inferior gluteal nerve supplies the gluteus maximus, while the gluteus medius and minimus are innervated by the superior gluteal nerve.

The arterial supply to the gluteal region is derived from the gluteal arteries which make this area an important anastomosis site between the femoral and the internal iliac artery. The piriformis muscle is an important landmark for neurovasculature in the gluteal region.

Posterior thigh muscles

Posterior thigh muscles are the lateral rotators of the hip, namely,

  • the piriformis,
  • gemelli (superior and inferior),
  • obturator internus and quadrates femoris, and
  • the ‘hamstrings’.

The hamstrings bring about flexion of the knee and extension of the hip joint. The semimembranosus, semitendinosus and long head of biceps femoris constitute the hamstrings. The tibial component of the sciatic nerve supplies the hamstrings.

Popliteal fossa

Thigh cross section reveals the 3 compartments of the thigh, namely, the anterior, posterior and the medial compartment. While the anterior compartment muscles bring about mainly extension of the knee and are supplied by the femoral nerve, the posterior compartment muscles are responsible for flexion and are innervated by the tibial nerve. The adductors rule the medial compartment and receive innervations by the obturator nerve.

The diamond-shaped, fat-filled cavity behind the knee joint is bound by the gastrocnemius, and the hamstrings. While the popliteal fascia and skin constitute the roof of this fossa, the floor comprises of the popliteal surface of femur, popliteal fascia and muscle.

The contents of the popliteal fossa are:

  • The small saphenous vein
  • popliteal artery and associated branches
  • tibial and common fibular nerves
  • posterior cutaneous nerve of the thigh
  • popliteal lymph nodes
  • fat

Review Questions

1. Which of the following is not the content of the popliteal fossa?

  1. Tibial nerve
  2. Fat
  3. Small saphenous artery
  4. Common fibular nerve

2. Which of the following is a part of the cruciate anastomosis in the gluteal region?

  1. First perforating artery: ascending branch
  2. Fourth perforating artery: ascending branch
  3. Third perforating artery: ascending branch
  4. Second perforating artery: ascending branch

3. Identify the insertion site of the piriformis muscle.

  1. Lesser trochanter
  2. Greater trochanter
  3. Ischial spine
  4. Iscial tiberosity
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