Introduction

This study guide summarizes the anatomy and physiology of the muscles of the hip and thigh, focusing on their structure, function, and compartmental organization. It is based on Lecture 15 of ANAT1005 and relevant textbook readings. Understanding these muscle groups is essential for comprehending lower limb movement and clinical applications.

Etymology: Useful Word Roots for Key Terms

Understanding the etymology of anatomical terms aids in memorization and comprehension.

• Genu (L): knee

• Coxa (L): hip

• Crus/crura (L): leg

• Fibula (L): pin, clasp, or buckle

• Glutos (G): rump, buttock

• Gracilis (L): slender

• Rectus (L): straight

• Vastus (L): vast

• Biceps (L): two heads

• Pecten (L): comb (e.g., pectineus)

• Gemellus (L): twin/doubled

• Obturator: closed over (refers to obturator foramen)

• Acetabulum (L): vinegar cup (hip socket)

Learning Objectives

• Recognize and understand muscle compartments and groups: structure and function

• Describe the deep fascia, including fascia lata and iliotibial tract

• Identify the inguinal ligament and femoral triangle

• Understand biarticular (two-joint) muscles affecting both hip and knee (e.g., hamstrings, quadriceps)

• Know the origins and insertions for muscles of the thigh and leg

Approach to Learning

1. Generalities: Learn muscle groups/compartments and their common actions.

2. Basics for Each Muscle: Locate each muscle on the skeleton and body; understand specific actions based on attachments.

3. Specifics: Master detailed origins, insertions, and unique features.

Overview of Regions & Compartments

Muscle Groups of the Lower Limb

• Hip Region:

  • Gluteal muscles (posterior, buttocks)

  • Hip flexors (anterior, deep)

• Thigh Compartments:

  • Anterior thigh (quadriceps group)

  • Posterior thigh (hamstrings group)

  • Medial thigh (adductors group)

• Leg Compartments:

  • Anterior leg

  • Posterior leg (superficial and deep layers)

  • Lateral leg

• Foot Groups:

  • Plantar intrinsic foot muscles (4 layers)

  • Dorsal intrinsic foot muscles (2 extensors)

Deep Fascia of the Lower Limb

• Fascia lata: Well-developed deep fascia of the thigh, providing compartmentalization and support.

• Iliotibial tract (IT band): Thickened lateral band of fascia lata, running down the lateral thigh, functioning as a tendon and supporting structure.

Muscles of the Hip

Anterior Hip Group

This group consists of three muscles primarily responsible for hip flexion.

• Iliacus

  • Origin: Iliac fossa of the ilium

  • Insertion: Lesser trochanter of the femur

  • Function: Flexes the hip joint and lumbar vertebral column

• Psoas major

  • Origin: Bodies and transverse processes of lumbar vertebrae

  • Insertion: Lesser trochanter of the femur (with iliacus, forms iliopsoas)

  • Function: Flexes the hip joint and lumbar vertebral column

• Psoas minor

  • Origin: T12-L1 vertebrae

  • Insertion: Pelvic brim

  • Function: Does not act on the hip joint

Posterolateral Hip Groups: Gluteal Region

These muscles are primarily responsible for hip extension, abduction, and lateral rotation.

Superficial Layer

• Gluteus maximus: Extends and laterally rotates the hip

• Gluteus medius: Abducts and medially rotates the hip

• Gluteus minimus: Abducts and medially rotates the hip

• Tensor fascia latae: Tenses the fascia lata, assists in abduction and medial rotation

Deep Layer (Lateral Rotators)

• Piriformis

• Gemellus superior

• Obturator internus

• Gemellus inferior

• Obturator externus

• Quadratus femoris

Common function: Lateral rotation of the hip joint

Muscles of the Thigh

Anterior Thigh Muscles (Quadriceps + Sartorius)

These muscles primarily extend the knee and flex the hip.

• Sartorius

  • Origin: Anterior superior iliac spine (ASIS)

  • Insertion: Medial, proximal tibia

  • Function: Flexes, abducts, and laterally rotates the hip; flexes the knee

• Quadriceps femoris (four heads):

  • Rectus femoris: Flexes hip and extends knee

  • Vastus lateralis: Extends knee

  • Vastus medialis: Extends knee

  • Vastus intermedius: Extends knee

Medial Thigh Muscles (Adductors)

These muscles adduct the femur at the hip joint.

• Pectineus

• Adductor longus

• Adductor brevis

• Adductor magnus

• Gracilis

Femoral Triangle

• Superior border: Inguinal ligament

• Lateral border: Sartorius

• Medial border: Adductor longus

• Floor: Pectineus and iliopsoas

• Roof: Fascia lata, superficial fascia, and skin

Posterior Thigh Muscles (Hamstrings)

These muscles extend the hip and flex the knee.

• Biceps femoris (long and short heads)

  • Origin: Long head from ischial tuberosity; short head from femur

  • Insertion: Head of fibula

  • Function: Extends hip (long head), flexes knee (both heads)

• Semitendinosus

  • Origin: Ischial tuberosity

  • Insertion: Medial, proximal tibia

  • Function: Extends hip, flexes knee

• Semimembranosus

  • Origin: Ischial tuberosity

  • Insertion: Medial condyle of tibia

  • Function: Extends hip, flexes knee

Review: Movements

Muscles That Move the Hip (Coxal) Joint

• Flexion: Iliopsoas, rectus femoris, sartorius

• Extension: Gluteus maximus, hamstrings

• Abduction: Gluteus medius, gluteus minimus, tensor fascia latae

• Adduction: Adductor group, gracilis

• Lateral rotation: Deep gluteal muscles (lateral rotators)

• Medial rotation: Gluteus medius, gluteus minimus

Muscles That Move the Knee Joint

• Extension: Quadriceps femoris group

• Flexion: Hamstrings group, sartorius, gracilis

Summary Table: Major Muscles of the Hip and Thigh

Key Equations and Concepts

• Muscle force and movement: The action of a muscle depends on its origin, insertion, and the joint(s) it crosses.

• Biarticular muscles: Muscles that cross two joints can produce movement at both (e.g., rectus femoris, hamstrings).

References

• Marieb et al. (2019) Human Anatomy and Physiology

• Moore and Dalley (1999) Clinically Oriented Anatomy

• Other standard anatomy texts as listed in the lecture