Session 4b - Muscles Of The Gluteal Region And Thigh And Neurovascular Of The Thigh

Question 1

What does the gluteal region contain?

Answer 1

The gluteal region contains two groups of muscles: a superficial group, and a deep group.

Question 2

What are the superficial gluteal muscles?

Answer 2

Superficial gluteal muscles
This group comprises four muscles:
● Gluteus maximus
● Gluteus medius
● Gluteus minimus
● Tensor fascia latae (this muscle is displayed on the image of the anterior thigh later in this handbook due to its location in the thigh).

Question 3

What is the gluteus maximus like?

Answer 3

Gluteus maximus is the most superficial muscle. It has several proximal attachments. It is attached to the most posterior parts of the posterior surface of the ilium, the sacrotuberous ligament and the sacrum. Distally, most fibres insert into the iliotibial band, with a smaller proportion attaching onto the gluteal tuberosity (note, this is not the same as the greater trochanter). Gluteus maximus is an extensor of the hip and is important for standing from a sitting position, and also acts as an external rotator of the hip. Because it inserts onto the iliotibial tract, it stabilises the knee joint too.

Question 4

Where are the gluteus medius and minimus located?

Answer 4

Gluteus medius is deep to maximus. Gluteus minimus is deep to medius. These muscles have similar points of attachment to the posterior ilium and they both insert onto the greater trochanter. Because of their similar bony attachments, they move the hip in the same way – they abduct and internally rotate it.

Question 5

What role does gluteus medius and minimus play?

Answer 5

Gluteus medius and minimus play an important role in normal gait. When we walk or run, for much of the time we have only one leg in contact with the ground and the other is off the ground. When we stand on one leg, gluteus medius and minimus in the limb that we are standing on contract and hold the pelvis ‘level’, so that it does not tilt to the side that is unsupported (i.e. the side with the leg off the ground). If gluteus medius and minimus are weak or paralysed in one limb, the pelvis tilts down on the contralateral side every time the contralateral leg is off the ground, resulting in a limp.

Question 6

Where is the tensor fascia latae (TFL)?

Answer 6

Tensor fascia latae (TFL, tensor of the fascia lata) is attached to the ASIS and inserts into the iliotibial band, which itself inserts onto the lateral part of the proximal tibia. It acts as its name suggests – contraction of the muscle tenses the fascia lata and the iliotibial band. It stabilises the knee when it is extended and it also weakly flexes the hip joint. The fascia lata is a thick fascia that envelops the muscles of the thigh, from the iliac crest proximally, to the tibia distally. There is a thickening of the fascia lata laterally known as the iliotibial band.

Question 7

What are the superficial gluteal muscles innervated by?

Answer 7

The superficial gluteal muscles are innervated by the gluteal nerves which leave the sacral plexus in the pelvis via the greater sciatic foramen:
● Gluteus maximus is innervated by the inferior gluteal nerve.
● Gluteus medius and minimus, and TFL, are innervated by the superior gluteal nerve.

Question 8

What are the deep gluteal muscles?

Answer 8

Deep gluteal muscles
The deep gluteal muscles are small muscles that primarily stabilise and laterally rotate the hip joint. They are:
● Piriformis
● The superior and inferior gemelli
● Obturator internus
● Quadratus femoris
They all insert onto, or close to, the greater trochanter.

Question 9

What is the piriformis?

Answer 9

Piriformis is a key landmark. It attaches to the anterior surface of the sacrum, passes through the greater sciatic foramen, and inserts on the greater trochanter. The nerves of the sacral plexus are located on its surface in the pelvis. The sciatic nerve emerges below its inferior border in the gluteal region.

Question 10

Where do other deep gluteal muscles arise from?

Answer 10

The other deep gluteal muscles arise from the ischium, except for obturator internus, which arises from the obturator membrane. Its tendon passes through the lesser sciatic foramen.

Question 11

What muscles are in the anterior thigh?

Answer 11

The anterior compartment of the thigh contains seven muscles. As a group they primarily act as extensors of the knee and some of them act upon the hip joint. They are all innervated by the femoral nerve (derived from spinal nerves L2-L4).

Question 12

What are the muscles of the anterior thigh?

Answer 12

The muscles are:
● Quadriceps femoris – a group of four large muscles.
● Sartorius
● Iliopsoas
● Pectineus.

Question 13

What is the quadriceps femoris?

Answer 13

Quadriceps femoris
This is the primary extensor of the knee, and this group forms the bulk of the anterior thigh:
● Rectus femoris
● Vastus lateralis
● Vastus medialis
● Vastus intermedius.

Question 14

Where does the quadriceps femoris converge?

Answer 14

These four muscles converge onto the quadriceps tendon which runs over the patella (kneecap) to insert onto the tibial tuberosity via the patellar ligament.

Question 15

Where do the muscles in the quadriceps femoris lie?

Answer 15

• Rectus femoris lies in the midline of the anterior thigh. It is attached to the AIIS proximally. Because it crosses the hip, it can also contribute to flexion of the hip.
• Vastus lateralis lies lateral to rectus femoris. It attaches to the linea aspera on the posterior aspect of the femoral shaft.
• Vastus medialis lies medial to rectus femoris. It also attaches to the linea aspera.
• Vastus intermedius lies deep to rectus femoris. It attaches to the anterior aspect of the femoral shaft.

Question 16

Where is the sartorius located?

Answer 16

Sartorius is located superficially in the anterior thigh. Its name is derived from the Latin word for ‘tailor’, as a reference to how tailors used to often sit in a cross-legged position, which is a demonstration of this muscle’s actions. It attaches proximally at the ASIS and twists across the thigh to insert on the medial aspect of the proximal tibia. It crosses both the hip and knee joints, so it is able to flex and externally rotate the hip joint and flex the knee joint. Sartorius is not the primary mover of these joints, but rather contributes to more delicate control.

Question 17

Where is the iliopsoas located?

Answer 17

Iliopsoas is located proximally in the anterior thigh. Psoas major and iliacus converge via a common tendon onto the lesser trochanter of the femur. Their names are merged into iliopsoas due to their shared attachment and function and it is the primary flexor of the hip joint. Psoas major is innervated directly by branches of the L1-L3 spinal nerves. Iliacus is innervated by the femoral nerve.

Question 18

Where is the pectineus?

Answer 18

Pectineus is located in the proximal anterior thigh, medial to iliopsoas. Some consider it a muscle of the anterior thigh, whilst others consider it part of the medial thigh, because it has features of both. It attaches proximally at the superior pubic ramus and distally on the femur, just inferior to the lesser trochanter, and it flexes and adducts the hip joint.

Question 19

What does the medial compartment of the thigh contain?

Answer 19

The medial compartment of the thigh contains five muscles. As a group they primarily act as adductors of the hip and are innervated by the obturator nerve (spinal nerves L2-L4).

Question 20

What are the muscles of the medial thigh?

Answer 20

The adductors play an important role in normal gait as they help to draw the leg towards the midline as we walk. The muscles of the medial thigh are:
● Adductor brevis
● Adductor longus
● Adductor magnus
● Gracilis
● Obturator externus
(As mentioned, some consider pectineus to be part of the medial compartment).

Question 21

What is the attachment of the adductor brevis and adductor longus?

Answer 21

Adductor brevis and adductor longus have similar points of attachment to the pubic bone and the linea aspera. Adductor brevis is deep to longus. The obturator nerve is between them.

Question 22

What is the adductor Magnus like?

Answer 22

Adductor magnus is a large muscle that has an adductor part and a hamstring part. These two parts function differently and have different nerve supplies:
● The adductor part attaches to the inferior pubic ramus and the linea aspera. It acts as an adductor and is innervated by the obturator nerve.
● The hamstring part attaches to the ischial tuberosity and the adductor tubercle. It acts as an extensor of the hip and is innervated by the tibial part of the sciatic nerve.

Question 23

What is the adductor hiatus?

Answer 23

The adductor hiatus is a gap formed between the distal attachments of the two parts of adductor magnus. The femoral artery and vein travel through the adductor hiatus to enter the posterior thigh.

Question 24

Where is the gracilis?

Answer 24

Gracilis is the most medial muscle. It attaches to the pubic bone and the medial aspect of the tibia. It is a weak adductor and flexor of the hip and a weak flexor of the knee.

Question 25

Where is the obturator externus?

Answer 25

Obturator externus is attached to the external surface of the obturator membrane and inserts on the femur near the greater trochanter. It stabilises and laterally rotates the hip joint.

Question 26

What muscles lie in the posterior thigh?

Answer 26

The posterior compartment of the thigh contains four muscles. These are:
● Semimembranosus and semitendinosus
● Biceps femoris (a long and a short head)
● Hamstring part of adductor magnus

Question 27

What are the hamstring muscles?

Answer 27

Three of these muscles - semimembranosus, semitendinosus, and the long head of biceps femoris - span both the hip and knee joints and are referred to as the ‘hamstrings’.

Question 28

What are the hamstrings attached to?

Answer 28

As a group, these muscles are attached proximally to the ischial tuberosity, they extend the hip and flex the knee and they are innervated by the tibial part of the sciatic nerve. Semimembranosus and semitendinosus insert on the medial aspect of the proximal tibia, whereas the long head of biceps femoris forms a common tendon with the short head and inserts onto the head of the fibula. The short head of biceps femoris arises from the linea aspera, therefore it flexes the knee, but does not move the hip joint. It is innervated by the common fibular part of the sciatic nerve.

Question 29

What does the hamstring part of the adductor Magnus arise from?

Answer 29

The hamstring part of adductor magnus arises from the ischial tuberosity and inserts onto the adductor tubercle of the femur, therefore it extends the hip but does not move the knee joint. It is innervated by the tibial part of the sciatic nerve.

Question 30

What are the boundaries of the femoral triangle?

Answer 30

The femoral triangle is a clinically important region of the proximal anterior thigh. It has notable boundaries:
● lateral - formed by the medial border of sartorius.
● medial - formed by the lateral border of adductor longus.
● superior - formed by the inguinal ligament.
● The apex is distal, where sartorius and adductor longus meet.
● The floor of the triangle is formed by iliopsoas laterally and pectineus medially.

Question 31

What are the contents of the femoral triangle?

Answer 31

● The femoral artery can be palpated and accessed for clinical procedures in the femoral triangle.
● The femoral vein is located medial to the femoral artery. It receives an important tributary in the femoral triangle – a superficial vein called the great saphenous vein.
● The femoral nerve is located lateral to the femoral artery. It travels deep to the inguinal ligament to enter the anterior thigh.

Question 32

Where are the femoral artery and vein located?

Answer 32

The femoral artery and vein are located superficially in the femoral triangle. This means they may be vulnerable to penetrating injuries, but they are also quite easily accessible for clinical procedures. Remembering the order of structures in the femoral triangle is vital when accessing them using a landmark or ultrasound-guided approach. From lateral to medial, they are Nerve, Artery, Vein. More medially, there are Lymphatics so the mnemonic NAVaL is used to remember the order from lateral to medial.

Question 33

What is the gluteal muscles suppled by posteriorly?

Answer 33

Posteriorly, the gluteal muscles are supplied by the superior and inferior gluteal arteries, which are branches of the internal iliac artery. They leave the pelvis via the greater sciatic foramen to enter the gluteal region.

Question 34

What is the femoral artery a continuation of?

Answer 34

Anteriorly, the femoral artery is the continuation of the external iliac artery. It travels deep to the inguinal ligament to enter the proximal anterior thigh. It is located relatively superficially here and can be palpated. It gives off a large branch called the profunda femoris (deep artery of the thigh) which travels deep into the thigh and supplies it. The femoral artery continues distally, traverses the adductor hiatus, and enters the distal part of the posterior thigh where it becomes the popliteal artery.

Question 35

What is the obturator artery a branch of?

Answer 35

Medially, the obturator artery is a branch of the internal iliac artery. It travels through the obturator canal into the medial compartment of the thigh. It anastomoses with branches from the femoral artery.

Question 36

What are the hamstring muscles supplied by?

Answer 36

There is no large artery in the upper posterior thigh. The hamstring muscles are supplied by three or four perforating arteries that arise from the profunda femoris. These perforating arteries travel through small apertures in the adductor magnus to reach the posterior compartment.

Question 37

What is the course of the gluteal veins?

Answer 37

Posteriorly, superior and inferior gluteal veins follow the corresponding arteries through the greater sciatic foramen into the pelvis. They drain into the internal iliac vein.

Question 38

What is the course of the femoral vein?

Answer 38

Anteriorly, the femoral vein follows the course of the femoral artery. It is located medial to the femoral artery in the proximal thigh. The femoral vein is a continuation of the popliteal vein after it leaves the popliteal fossa (behind the knee joint) and enters the anterior thigh via the adductor hiatus. This vessel – now the femoral vein – ascends through the anterior thigh. It receives the great saphenous vein in the femoral triangle before travelling under the inguinal ligament to become the external iliac vein.

Question 39

What is the course of the obturator vein?

Answer 39

The obturator vein follows the course of the obturator artery. It travels through the obturator canal and joins the internal iliac vein in the pelvis.

Question 40

What are the gluteal muscles innervated by?

Answer 40

The gluteal muscles are innervated by the superior and inferior gluteal nerves. These nerves leave the sacral plexus in the pelvis and travel through the greater sciatic foramen to enter the gluteal region.

Question 41

What is the course of the femoral nerve?

Answer 41

The femoral nerve is formed from the L2 - L4 spinal nerves. It travels deep to the inguinal ligament to enter the proximal anterior thigh lateral to the femoral artery. Branches innervate the anterior thigh muscles. The saphenous nerve is a sensory branch of the femoral nerve that innervates skin over the leg.

Question 42

What is the course of the obturator nerve?

Answer 42

The obturator nerve is also formed from the L2 – L4 spinal nerves. It travels along the lateral wall of the pelvis and exits through the obturator canal. It emerges onto the superficial surface of adductor brevis and gives rise to branches that innervate the medial compartment muscles and skin over the medial thigh.

Question 43

What is the course of the tibial nerve?

Answer 43

The tibial nerve innervates the muscles of the posterior thigh and posterior leg. The common fibular nerve innervates the muscles of the anterior and lateral leg. Thus, a lesion of the sciatic nerve can result in severe functional deficits.

Question 44

What is the course of the sciatic nerve?

Answer 44

The sciatic nerve is a large nerve composed of fibres from the L4 – S3 spinal nerves. It leaves the pelvis via the greater sciatic foramen and enters the gluteal region inferior to the lower border of piriformis. The nerve is really composed of two separate nerves bound together – the tibial nerve and the common fibular nerve.

Question 45

Where can the femoral artery be accessed?

Answer 45

The sciatic nerve is a large nerve composed of fibres from the L4 – S3 spinal nerves. It leaves the pelvis via the greater sciatic foramen and enters the gluteal region inferior to the lower border of piriformis. The nerve is really composed of two separate nerves bound together – the tibial nerve and the common fibular nerve.

Question 46

What is the fascia iliaca compartment block (FICB)?

Answer 46

This is a commonly performed procedure in the emergency department where a relatively large volume (around 30-40ml) of local anaesthetic is injected, usually under ultrasound guidance, just underneath the fascia of the iliacus muscle near the femoral triangle. In this ‘compartment’, there are several nerves that carry pain sensation from the around the neck of the femur, including the femoral and obturator nerves, so it is performed to provide analgesia (pain relief) to patients that have sustained a neck of femur fracture. Care must be taken not to accidentally inject the anaesthetic into an artery or vein.

Question 47

What is a femoral hernia?

Answer 47

Similar to an inguinal hernia, this is an abnormal protrusion of intestine into the upper anterior thigh. It is more common in females. The intestine passes deep to the inguinal ligament and causes a lump to appear just distal to the inguinal region. Strangulation of the herniated intestine leads to ischaemia and infarction of the tissue.

Question 48

What is an obturator nerve irritation?

Answer 48

Along its course on the lateral wall of the pelvis, the obturator nerve runs close to the ovary. Ovarian pathology, such as a cyst, may irritate the nerve. This typically results in sensory abnormalities (tingling, itching or pain) in the medial thigh.

Question 49

What is a gluteus maximus injection?

Answer 49

Gluteus maximus is a common site for intramuscular injection, but the sciatic nerve must be avoided. Given the position of the nerve deep to the gluteal muscles, the only safe place to give an injection is into the upper outer quadrant of the buttock to safely avoid the sciatic nerve.

Question 50

What is sciatica?

Answer 50

This term is in common use and describes pain that is felt in the posterior thigh and leg due to compression of nerve roots that contribute to the sciatic nerve (L4 - S3). Most commonly it is the result of a prolapsed (‘slipped’) intervertebral disc between L5 and S1.