Gluteal region and posterior region

Question 1

What are the articulations of the hip bones?

Answer 1

Sacroiliac joint – articulation with the sacrum.
Pubic symphysis – articulation between the left and right hip bones.
Hip joint – articulation with the head of femur

Question 2

What are the major bones of the pelvis?

Answer 2

The hip bone is composed of the three parts; the ilium, pubis and ischium.

Question 3

What are the major features of the ilium?

Answer 3

The body of the ilium forms the superior part of the acetabulum.
Immediately above the acetabulum, the ilium expands to form the wing (or ala).
Iliac crest - extends from the anterior superior iliac spine (ASIS) to the posterior superior iliac spine (PSIS).
On the posterior aspect of the ilium there is an indentation known as the greater sciatic notch.

Question 4

What are the surfaces of the wings of the ilium?

Answer 4

Inner surface – has a concave shape, which produces the iliac fossa (site of origin of the iliacus muscle).
External surface (gluteal surface) – has a convex shape and provides attachments to the gluteal muscles.

Question 5

What are the major features of the pubis?

Answer 5

Pubic body - articulates with the opposite pubic body at the pubic symphysis. Its superior aspect is marked by a rounded thickening (the pubic crest), which extends laterally as the pubic tubercle.
Superior pubic ramus – extends laterally from the body to form part of the acetabulum.
Inferior pubic ramus – projects towards the ischium.
The superior and inferior rami enclose part of the obturator foramen – through which the obturator nerve, artery and vein pass through to reach the lower limb.

Question 6

What are the major features of the ischium?

Answer 6

The inferior ischial ramus combines with the inferior pubic ramus forming the ischiopubic ramus, which encloses part of the obturator foramen.
The posteroinferior aspect of the ischium forms the ischial tuberosities and when sitting, it is these tuberosities on which our body weight falls.
Near the junction of the superior ramus and body is a posteromedial projection of bone; the ischial spine.

Question 7

What are the two important ligaments that attach to the ischium?

Answer 7

Sacrospinous ligament – runs from the ischial spine to the sacrum, thus creating the greater sciatic foramen through which lower limb neurovasculature (including the sciatic nerve) transcends.
Sacrotuberous ligament – runs from the sacrum to the ischial tuberosity, forming the lesser sciatic foramen.

Question 8

What are the two types of muscles in the gluteal region?

Answer 8

Superficial abductors and extensors – group of large muscles that abduct and extend the femur. Includes the gluteus maximus, gluteus medius, gluteus minimus and tensor fascia lata.
Deep lateral rotators – a group of smaller muscles that mainly act to laterally rotate the femur. Includes the quadratus femoris, piriformis, gemellus superior, gemellus inferior and obturator internus.

Question 9

What is the arterial supply and venous drainage in the gluteal region?

Answer 9

The arterial supply to these muscles is mostly via the superior and inferior gluteal arteries – branches of the internal iliac artery. Venous drainage follows the arterial supply.

Question 10

What is the gluteus maximus?

Answer 10

Largest and most superficial
Originates from the gluteal surface of the ilium, sacrum and coccyx and inserts into the iliotibial tract and the gluteal tuberosity of the femur.
It is the main extensor of the thigh, and assists with lateral rotation.
Innervated by the inferior gluteal nerve.

Question 11

What is the gluteus medius?

Answer 11

In between the gluteus maximus and minimus
Originates from the gluteal surface of the ilium and inserts into the lateral surface of the greater trochanter.
Abducts and medially rotates the lower limb. During locomotion, it secures the pelvis, preventing pelvic drop of the opposite limb.
Innervated by the superior gluteal nerve.

Question 12

What is the gluteus minimus?

Answer 12

Originates from the ilium and converges to form a tendon, inserting to the anterior side of the greater trochanter.
Abducts and medially rotates the lower limb. During locomotion, it secures the pelvis, preventing pelvic drop of the opposite limb.
Innervated by the superior gluteal nerve.

Question 13

What is the tensor fascia lata?

Answer 13

Originates from the anterior iliac crest, attaching to the anterior superior iliac spine (ASIS). It inserts into the iliotibial tract, which itself attaches to the lateral condyle of the tibia.
Assists the gluteus medius and minimus in abduction and medial rotation of the lower limb. It also plays a supportive role in the gait cycle.
Innervated by the superior gluteal nerve.

Question 14

What are the deep muscles of the gluteal region?

Answer 14

The deep gluteal muscles are a set of smaller muscles, located underneath the gluteus minimus. The general action of these muscles is to laterally rotate the lower limb. They also stabilise the hip joint by ‘pulling’ the femoral head into the acetabulum of the pelvis.

Question 15

What is the piriformis muscle?

Answer 15

Originates from the anterior surface of the sacrum. It then travels infero-laterally, through the greater sciatic foramen, to insert into the greater trochanter of the femur.
Lateral rotation and abduction.
Innervated by the piriformis nerve.

Question 16

What are the obturator internus?

Answer 16

Forms the lateral walls of the pelvic cavity.
Originates from the pubis and ischium at the obturator foramen. It travels through the lesser sciatic foramen, and attaches to the greater trochanter of the femur.
Lateral rotation and abduction.
Innervated by the nerve to obturator internus.

Question 17

What are the gemelli?

Answer 17

The gemelli are two narrow and triangular muscles. They are separated by the obturator internus tendon.
The superior gemellus muscle originates from the ischial spine, the inferior from the ischial tuberosity. They both attach to the greater trochanter of the femur.
Lateral rotation and abduction.
The superior gemellus muscle is innervated by the nerve to obturator internus, the inferior gemellus is innervated by the nerve to quadratus femoris.

Question 18

What is the quadratus femoris?

Answer 18

Most inferior of the deep gluteal muscles, located below the gemelli and obturator internus.
It originates from the lateral side of the ischial tuberosity, and attaches to the quadrate tuberosity on the intertrochanteric crest.
Lateral rotation
Nerve to quadratus femoris

Question 19

What are the key features of the muscles in the posterior compartment of the thigh?

Answer 19

The muscles in the posterior compartment of the thigh are collectively known as the hamstrings. They consist of the biceps femoris, semitendinosus and semimembranosus, which form prominent tendons medially and laterally at the back of the knee.
As a group, these muscles act to extend at the hip, and flex at the knee. They are innervated by the sciatic nerve (L4-S3).

Question 20

What is the biceps femoris?

Answer 20

The long head originates from the ischial tuberosity of the pelvis. The short head originates from the linea aspera on posterior surface of the femur. Together, the heads form a tendon, which inserts into the head of the fibula.
Main action is flexion at the knee. It also extends the thigh at the hip, and laterally rotates at the hip and knee.
Long head innervated by the tibial part of the sciatic nerve, whereas the short head is innervated by the common fibular part of the sciatic nerve.

Question 21

What is the semitendinosus?

Answer 21

It originates from the ischial tuberosity of the pelvis, and attaches to the medial surface of the tibia.
Flexion of the leg at the knee joint. Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint.
Innervated by the tibial part of the sciatic nerve.

Question 22

What is the semimembranosus?

Answer 22

It originates from the ischial tuberosity, but does so more superiorly than the semitendinosus and biceps femoris. It attaches to the medial tibial condyle.
Flexion of the leg at the knee joint. Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint.
Innervated by tibial part of the sciatic nerve.

Question 23

What is the pathway of the sciatic nerve?

Answer 23

Emerges from the greater sciatic foramen, under the piriformis muscle (deep to the gluteus maximus), runs along the long head of the biceps femoris and between the lateral and medial posterior thigh muscles to enter the popliteal fossa. Splits into tibial and common peroneal.

Question 24

What is the gluteal sulcus?

Answer 24

The gluteal sulcus (also known as the gluteal fold, fold of the buttock or horizontal gluteal crease) is an area of the body of humans and anthropoid apes, described by a horizontal crease formed by the inferior aspect of the buttocks and the posterior upper thigh.

Question 25

What is Sciatica?

Answer 25

The sciatic nerve arises from the nerve roots at L5 and S1-4. The intervertebral disc between L5 and S1 commonly prolapses and compresses the nerve in the intervertebral foramina. This leads to a referred pain which is felt down the skin of the lateral thigh and leg into the foot. This is the area of skin where sensation is transmitted by the sciatic nerve.

Question 26

What are safe and unsafe sites to inject into the buttock?

Answer 26

Injection in the lower medial quadrant of the buttock may damage the sciatic nerve and can lead to pain or paralysis. On the contrary in the upper outer quadrant of the buttock there is only muscle - good tissue for drug absorption (this is a safe site).

Question 27

What is a Popliteal aneurysm?

Answer 27

An aneurysm is where the arterial wall becomes diseases and the pressure of blood within the artery causes a swelling. They are not uncommon and lead to two serious problems:
Blood can clot in the aneurysm causing the artery to become blocked resulting in the death of the leg.
The swelling can get so big that the artery ruptures, this is common in aneurysms of the aorta and is usually fatal.

Question 28

What is the Trendelenburg test?

Answer 28

The gluteus medius and minimus both abduct the hip joint. During normal walking when one leg is lifted off the ground, the opposite gluteus muscles contract to support the pelvis in a horizontal position. If this contraction is insufficient then the pelvis will tilt and walking will be more difficult and looks abnormal, this is Trendelenburg test.