Gluteal Region Anatomy Notes

Lower Limb - Gluteal Region

Learning Objectives

Identify osteological features of the pelvis and pelvic girdle.
Recognize the joints and ligaments of the pelvis and pelvic girdle.
Identify osteological features of the hip and hip joint.
Recognize the ligaments of the hip joint.
Identify muscles of the gluteal region and understand their actions.

Osteology of the Gluteal Region

Pelvis: Consists of the ilium, ischium, pubis, sacrum, and coccyx.
Ilium: Bone in the pelvis.
Ischium: Bone in the pelvis.
Pubis: (or pubic bone): Bone in the pelvis.
Sacrum/coccyx: Bones in the pelvis.
Femur: Thigh bone.
The ilium, ischium, and pubis are fused together.
Many muscles and ligaments in the gluteal region attach to the femur and pelvis.

Osteology: Pelvis vs. Pelvic Girdle

Pelvis: Two hip bones (ilium, ischium, pubis), sacrum, and coccyx.
Pelvic Girdle: Two hip bones (ilium, ischium, pubis).
Pelvis consists of the two hip bones composed of the ilium, ischium, and pubis, as well as the sacrum and coccyx.
The pelvic girdle consists of the two bones (ilium, ischium, and pubis).

Key Osteological Features

Acetabulum: The socket where the head of the femur articulates with the pelvis, forming the hip joint. It is formed by the ilium, ischium, and pubis.
Anterior Superior Iliac Spine (ASIS): Palpable on the anterior side of the body.
Anterior Inferior Iliac Spine (AIIS): bony prominence.
Posterior Superior Iliac Spine (PSIS): Palpable on the posterior side of the body, though less easily than the ASIS.
Ischial Tuberosity: Also known as 'sit bones'.

Pelvic Girdle Functions

Transfer the weight of the upper body from the axial skeleton to the lower appendicular skeleton for standing and walking.
Withstand compression and other forces resulting from its support of body weight.
House and protect the pelvic viscera/organs.

Pelvic Osteology

The bony pelvis is divided into upper and lower portions by the pelvic brim.
- The upper portion (above the pelvic brim) is the false (greater) pelvis.
- The lower portion (below the pelvic brim) is the true (lesser) pelvis.
The upper opening of the true pelvis is the pelvic inlet.
The lower opening of the true pelvis is the pelvic outlet.

Pelvic Osteology – Male-Female Differences

Feature	Male	Female
General Structure	Thick and Heavy	Thin and Light
Greater Pelvis	Deep	Shallow
Lesser Pelvis	Narrow and Deep	Wide and Shallow
Pelvic Inlet	Heart-Shaped	Oval and Rounded
Pelvic Outlet	Small	Large
Pubic Arch	Narrow (<70)	Wide (>80)
Obturator Foramen	Round	Oval
Acetabulum	Large	Small

Female pelvis is designed for childbirth.
Male pelvis is designed for movement and to support a heavier body.
Additional variations can be seen based on ethnicity and genetics.

Test your Knowledge

What is your ‘butt bone’ (i.e., what do you ‘sit’ on)?
- b) Ischial tuberosity
What is the pelvic girdle composed of?
- b) Ilium, Ischium, Pubis

Joints and Ligaments of the Pelvis and Pelvic Girdle

Sacroiliac Joint: Articulation of the sacrum and ilium.
- Ligaments:
  - Anterior sacroiliac ligament
  - Posterior sacroiliac ligament (overlays the interosseous sacroiliac ligament)
  - Interosseous sacroiliac ligament: Likely contributes the most to keeping the joint together with the fiber orientation perpendicular to ileum and sacrum (short, strong fibers).
- Holds pelvis together, facilitating weight transfer from upper to lower body.
Pubic Symphysis:
- Cartilaginous joint
- Ligaments:
  - Superior pubic ligament
  - Inferior pubic ligament
- Weak point of the pelvis; commonly injured in car accidents.
Lumbosacral Ligament:
- Attaches to the L5 vertebra and sacrum anteriorly.
Iliolumbar Ligament:
- Attaches to the L5 vertebra and iliac crest.
Inguinal Ligament:
- Runs from the ASIS to the pubic tubercle; acts as a site for many muscle attachments.
Sacrospinous Ligament:
- Attaches the sacrum to the ischial spine.
Sacrotuberous Ligament:
- Attaches the sacrum to the ischial tuberosity.
The sacrospinous and sacrotuberous ligaments prevent the sacrum from tilting upward, inhibiting the anterior collapse of the pelvis.

Purpose of the Pelvis and Pelvic Girdle - Ligaments

Support weight of upper body by transferring it to the lower limbs.
Attachment points for muscles.
Protect pelvic organs.
Provide Stability.

Test your Knowledge

What joint is very weak in the pelvis?
- Pubic symphysis
List the ligaments of the pelvis and pelvic girdle. What is the function of these ligaments in association with the pelvis?
- Sacroiliac ligaments (anterior, posterior, interosseous), superior and inferior pubic ligaments, sacrospinous ligaments, sacrotuberous ligaments, iliolumbar ligaments, lumbosacral ligaments, inguinal ligaments
  - FUNCTIONS:
    - Support weight of upper body by transferring to lower limbs
    - Attachment points for muscles
    - Protect pelvic organs
    - Stability

Osteology of the Proximal Femur

Head: Articulates with the acetabulum of the pelvis.
- Fovea: Location where blood supply enters.
Neck: Connects the head to the shaft.
Greater Trochanter: Large prominence located laterally.
Lesser Trochanter: Smaller prominence located medially and inferiorly to the greater trochanter.
Intertrochanteric Line: Located anteriorly between the trochanters.
Intertrochanteric Crest: Located posteriorly between the trochanters.
Trochanteric Fossa
Spiral Line
Gluteal Tuberosity: Located on the posterior aspect.
Linea Aspera: Prominent ridge running along the posterior aspect of the femur.

Osteology of the Hip Joint

The head of the femur articulates with the acetabulum of the pelvis.

Test your Knowledge

The of the femur articulates with the of the pelvis, creating the hip joint.
- Head; acetabulum
The linea aspera is on the __ aspect of the femur:
- c) posterior

Hip Joint

Ball and socket joint: allows flexion/extension, adduction/abduction, external/internal rotation, and circumduction.
Articulation between the head of the femur and acetabulum.
Reinforced by iliofemoral, ischiofemoral, and pubofemoral ligaments.
Ligamentum capitis femoris (ligamentum teres) helps attach the femoral head into the acetabulum.
The ball-and-socket joint can perform movements in all three planes (frontal, sagittal, transverse) and axes (anteroposterior, mediolateral, longitudinal).

Hip Joint Stability

The acetabulum (socket) is deeper than the glenoid cavity (shoulder), making the hip more stable than the shoulder.

Ligaments of the Hip Joint

Iliofemoral Ligament:
- Attaches to the anterior inferior iliac spine and acetabular rim proximally and the intertrochanteric line distally.
- Prevents hyperextension of the hip during standing by screwing the femoral head into the acetabulum.
Pubofemoral Ligament:
- Arises from the obturator crest of the pubic bone and passes laterally and inferiorly to merge with the fibrous layer of the joint capsule.
- Tightens during extension and abduction of the hip joint.
Ischiofemoral Ligament:
- Weak compared to the others.
- Arises from the ischial part of the acetabular rim and spirals superiolaterally to the neck of the femur, medial to the base of the greater trochanter.

These three ligaments stabilize the hip joint and keep the head of the femur in the acetabulum.

Test your Knowledge: MATCHING

Iliofemoral ligament: 1, 6
- Attaches to the anterior, inferior iliac spine and acetabular rim proximally and the intertrochanteric line distally
- Prevents hyperextension of the hip during standing by screwing the femoral head into the acetabulum
Pubofemoral ligament: 3, 4
- Arises from obturator crest of the pubic bone and passes laterally and inferiorly to merge with the fibrous layer of the joint capsule
- Tightens during extension and abduction of hip joint
Ischiofemoral ligament: 2, 5
- Weak
- Arises from ischial part of acetabular rim and spirals superiolaterally to the neck of the femur, medial to the base of the greater trochanter

Muscles of the Gluteal Region - Overview

Piriformis
Obturator Internus
Obturator Externus
Gemellus Superior
Gemellus Inferior
Quadratus Femoris
Gluteus Minimus
Gluteus Medius
Gluteus Maximus

Be able to identify/name/draw/indicate the action of these muscles.

Movements of the Hip Joint

Flexion and extension (Sagittal Plane)
Abduction and adduction (Frontal plane)
Internal and external rotation (Transverse Plane)
The hip joint is a ball-and-socket joint so it can act/create movement in all three planes (frontal, sagittal, transverse) about the three axes (anteroposterior, mediolateral, longitudinal).

Muscles of the Gluteal Region

Piriformis

Origin: Anterior surface of sacrum between anterior sacral foramina
Insertion: Medial side of the superior border of greater trochanter of femur
Action: External rotation of the extended hip (standing up), and abduction of the flexed hip
Innervation: Nerves from L5, S1, S2
Piriformis travels through the great sciatic foramen along with the sciatic nerve

Injury to the Sciatic Nerve

Pain in buttock:
- Reason: Compression of the sciatic nerve via piriformis
Sciatica:
- Symptoms: Pain travels from buttocks down the leg
- Reason: Herniated disc or overgrowth of bone puts pressure on the lumbar spine nerve roots

Muscles of the Gluteal Region

Obturator Internus

Origin: Deep surface of obturator membrane and surrounding bone
Insertion: Medial surface of greater trochanter of femur
Action: External rotation of extended hip and abduction of flexed hip
Innervation: Nerves from L5 and S1

Obturator Externus

Origin: External surface of obturator membrane and adjacent bone
Insertion: Trochanteric fossa of femur
Action: External rotation of hip
Innervation: Obturator nerve

Muscles of the Gluteal Region

Gemellus Superior

Origin: external surface of ischial spine
Insertion: medial side of greater trochanter of femur (with obturator internus tendon)
Action: External rotation of the extended hip, and abduction of the flexed hip
Innervation: Nerves from L5, S1 (nerve to obturator internus)

Gemellus Inferior

Origin: Upper aspect of ischial tuberosity
Insertion: Medial side of greater trochanter of femur (with obturator internus tendon)
Action: External rotation of the extended hip, and abduction of the flexed hip
Innervation: nerves from L5, S1 (nerve to quadratus femoris)

Muscles of the Gluteal Region

Quadratus Femoris

Origin: lateral aspect of ischium (anterior to ischial tuberosity)
Insertion: quadrate tubercle on intertrochanteric crest of femur
Action: External rotation of the hip, and adduction of hip
Innervation: nerves from L5, S1 (nerve to quadratus femoris)

Muscles of the Gluteal Region

Gluteus Minimus

Origin: gluteal surface of ilium between inferior and anterior gluteal lines
Insertion: anterolateral aspect of greater trochanter of femur
Action: internal rotation and abduction of hip, support pelvis during gait
Innervation: superior gluteal nerve

Muscles of the Gluteal Region

Gluteus Medius

Origin: gluteal surface of ilium between anterior and posterior gluteal lines
Insertion: lateral surface of greater trochanter of femur
Action: internal rotation and abduction of hip, support pelvis during gait
Innervation: superior gluteal nerve

Muscles of the Gluteal Region

Gluteus Maximus

Origin: Fascia covering gluteus medius; gluteal surface of ileum behind posterior gluteal line; lumbar fascia; posterior inferior sacrum and coccyx; sacrotuberous ligament
Insertion: Posterior aspect of iliotibial band; gluteal tuberosity of femur
Action: Hip extension and external rotation (some hip abduction), stabilize hip
Innervation: Inferior gluteal nerve

Muscles of the Gluteal Region

Tensor Fasciae Latae

Origin: Anterior superior iliac spine; anterior iliac crest
Insertion: Iliotibial tract, which attaches to lateral condyle of tibia (Gerdy’s tubercle)
Action: Flexes hip joint, some hip abduction, internal hip rotation; stabilizes the extended knee
Innervation: Superior gluteal nerve

Test your Knowledge

Sort the gluteal region muscles into the following categories:
- Hip Flexion
- Hip Extension
- Hip Internal Rotation
- Hip External Rotation
- Hip Abduction
- Hip Adduction

Test your Knowledge: ANSWERS

Sort the gluteal region muscles into the following categories:
- Hip Flexion
- Hip Extension
  - Gluteus maximus
- Hip Internal Rotation
  - Gluteus minimus
  - Gluteus medius
- Hip External Rotation
  - Piriformis (extended)
  - Obturator Internus (extended)
  - Obturator Externus
  - Gemellus Superior (extended)
  - Gemellus Inferior (extended)
  - Quadratus Femoris
  - Gluteus maximus
- Hip Abduction
  - Piriformis (flexed)
  - Obturator Internus (flexed)
  - Gemellus Superior (flexed)
  - Gemellus Inferior (flexed)
  - Gluteus minimus
  - Gluteus medius
  - Gluteus maximus (some)
- Hip Adduction
  - Quadratus Femoris

Summary

Pelvis and Pelvic Girdle Joints/Ligaments

Sacroiliac joint
- Anterior, posterior, interosseous ligaments
- Hold pelvis together, facilitating weight transfer from upper to lower body
Pubic symphysis – cartilaginous joint
- Superior and inferior pubic ligaments
Lumbosacral joint/ligament
Iliolumbar joint/ligament
Sacrospinous and Sacrotuberous ligaments
- Prevent the anterior collapse of the pelvis
Iliofemoral ligament
Pubofemoral ligament
Ischiofemoral ligament
- Keeps the head of the femur in the acetabulum, aiding in stability of the joint and prevention of excessive joint motion

Summary

Piriformis
Obturator Internus
Obturator Externus
Gemellus Superior
Gemellus Inferior
Quadratus Femoris
Gluteus Minimus
Gluteus Medius
Gluteus Maximus

Difference between pelvis and pelvic girdle
Osteology
- Ilium
- Ischium
- Pubis
Identify/name/draw
Action