Lower Extremity Anatomy and Kinesiology Notes

Introduction

This comprehensive study guide covers the anatomy and movements of the lower extremity, focusing on the hip joint, gluteal region, and thigh compartments. It details muscle actions, attachments, innervations, and the neurovascular structures essential for understanding lower extremity function.

Learning Objectives

Upon reviewing these notes, you should be able to:

  • Describe the various movements possible at the hip joint.

  • Detail the structure of the hip joint, including its associated ligaments and cartilage.

  • Identify the muscles of the gluteal region and thigh, specifying their innervation, bony attachment points, and primary actions.

  • Describe the distinct compartments of the thigh and their respective contents.

  • Explain the anatomical relationships and contents of the femoral triangle.

Osteology (Thigh and Gluteal Region)

Specific osteological details of the pelvis and femur, including landmarks such as the iliac crest, ASIS, AIIS, ischial tuberosity, acetabulum, greater and lesser trochanters, gluteal tuberosity, and the linea aspera, are covered in the dry lab sessions. This foundational knowledge is crucial for understanding muscle attachments and joint mechanics.

Regions of the Lower Extremity

For anatomical study, the lower extremity is divided into several regions:

  • Hip

  • Gluteal Region

  • Thigh

  • Knee

  • Popliteal Region

  • Anterior Leg (Crural)

  • Posterior Leg (Sural)

  • Ankle

  • Foot (Dorsum and Plantar Surface)

Hip Joint

Movements of the Hip

The hip joint is a ball and socket synovial joint, allowing for a wide range of motion:

  • Flexion

  • Extension

  • Abduction

  • Adduction

  • Internal (Medial) Rotation

  • External (Lateral) Rotation

  • Circumduction (a combination of the above movements)

Hip Internal Structures

Key internal structures contributing to the hip joint's stability and function include:

  • Acetabular Labrum: A fibrocartilaginous rim that deepens the acetabulum and enhances joint congruity.

  • Acetabular Fossa: A non-articular part of the acetabulum.

  • Lunate Surface: The articular surface of the acetabulum.

  • Transverse Acetabular Ligament: Spans the acetabular notch, completing the acetabular rim.

  • Ligament of the Head of the Femur (Ligamentum Teres): Contains the artery of the ligament of the head of the femur, providing some vascular supply to the femoral head, especially in children. It's enclosed within a synovial sleeve.

Hip Ligaments and Fibrous Capsule

The hip joint's fibrous capsule is reinforced by several strong ligaments:

  • Iliofemoral (Y) Ligament: Located anteriorly, it is considered the strongest ligament in the body. It prevents hyperextension of the hip.

  • Pubofemoral Ligament: Also located anteriorly and inferiorly, it prevents excessive abduction and hyperextension.

  • Ischiofemoral Ligament: Located posteriorly, it is the weakest of the three capsular ligaments and prevents internal rotation and hyperextension. The fibrous capsule is generally strong anteriorly but weaker posteriorly.

Gluteal Region

Muscles of the Gluteal Region

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

Muscle Name

Principal Action(s)

Distal Attachment(s)

Innervation

Gluteus Maximus

Prime extensor of Hip, Hip Lateral Rotation

Gluteal tuberosity & IT band

Inferior gluteal n.

Gluteus Medius

Abduction of Hip, Stabilization of Pelvis during gait

Greater trochanter

Superior gluteal n.

Gluteus Minimus

Abduction of Hip, Stabilization of Pelvis during gait

Greater trochanter

Superior gluteal n.

Tensor fasciae latae

Tenses the fascia lata (IT band)

IT band

Superior gluteal n.

Deep Six Rotators of the Hip (PGOGOQ)

These muscles are deep to the gluteus medius and minimus and primarily contribute to lateral rotation of the hip. They all generally attach distally to the greater trochanter.

Muscle Name

Principal Action(s)

Distal Attachment(s)

Innervation

Piriformis

Lateral rotation of Hip

Greater trochanter

Spinal nn. L5-S2

Gemellus Superior

Lateral rotation of Hip

Greater trochanter

Spinal nn. L5-S1

Obturator Internus

Lateral rotation of Hip

Greater trochanter

Spinal nn. L5-S1

Gemellus Inferior

Lateral rotation of Hip

Greater trochanter

Spinal nn. L5-S1

Obturator Externus

Lateral rotation of Hip

Greater trochanter

Obturator nerve (not listed in original table, inferred from context)

Quadratus Femoris

Lateral rotation of Hip

Intertrochanteric crest

Spinal nn. L5-S1

Compartments of the Thigh

An important principle for the thigh compartments is "ONE COMPARTMENT, ONE NERVE," meaning each major compartment is primarily innervated by a specific nerve.

Anterior Compartment

Contents

  • Muscles: Iliopsoas (Iliacus, Psoas major), Sartorius, Pectineus, Quadriceps Femoris group.

  • Principal Actions: Primarily flex at the hip joint and extend at the knee joint.

  • Innervation: Predominantly by the Femoral nerve, with Psoas major also receiving innervation from spinal nerves L2-L4.

  • Neurovasculature: Femoral nerve, Femoral artery, Femoral vein, Lymphatics.

Muscles and Attachments

Muscle Group/Name

Proximal Attachment(s)

Distal Attachment(s)

Iliopsoas

Lesser trochanter

  Iliacus

Iliac fossa

 

  Psoas major

Lumbar vertebrae

 

Sartorius

Anterior superior iliac spine

Pes Anserine

Pectineus

Pubis (not tested)

Femur

Quadriceps Femoris

Tibial tuberosity via patellar ligament

  Rectus Femoris

Anterior inferior iliac spine

 

  Vasti muscles

Femoral shaft

 

Femoral Triangle

The femoral triangle is a clinically important anatomical space in the anterior thigh.

  • Superior Border: Inguinal ligament

  • Medial Border: Adductor Longus muscle

  • Lateral Border: Sartorius muscle

  • Floor: Pectineus and Iliopsoas muscles

  • Contents (from lateral to medial): Nerve (Femoral), Artery (Femoral), Vein (Femoral), Lymphatics (acronym: NAVL)

Femoral Sheath

The femoral sheath is a fascial tunnel formed by deep investing fascia. It encloses the femoral artery, femoral vein, and lymphatics, but it does not enclose the femoral nerve.

Posterior Compartment

Contents

  • Muscles: Hamstring muscle group (Biceps Femoris - long & short heads, Semimembranosus, Semitendinosus).

  • Principal Actions: Primarily extend at the hip joint and flex at the knee joint.

  • Innervation: Sciatic nerve.

Muscles and Attachments

Muscle Group/Name

Proximal Attachment(s)

Distal Attachment(s)

Biceps Femoris

Fibula

  Long head

Ischial tuberosity

 

  Short head

Shaft of the femur

 

Semimembranosus

Ischial tuberosity

Medial tibial condyle

Semitendinosus

Ischial tuberosity

Pes Anserine

Medial (Adductor) Compartment

Contents

  • Muscles: Adductor muscle group (Adductor Brevis, Adductor Longus, Adductor Magnus), Gracilis.

  • Principal Actions: Primarily adduction of the hip and slight medial rotation. Also function as posture stabilizing muscles.

  • Innervation: Obturator nerve.

  • Neurovasculature: Obturator nerve, Great saphenous vein (superficial to the compartment).

Muscles and Attachments

Muscle Group/Name

Proximal Attachment(s)

Distal Attachment(s)

Adductor Brevis

Pubis

Femur

Adductor Longus

Near pubic symphysis

Femur

Adductor Magnus

  Adductor 'fleshy' part

Ischium and pubis

Femur

  Hamstring 'tendinous' part

Ischial tuberosity

Adductor tubercle

Gracilis

Pubis

Pes Anserine

Thigh Compartment Breakdown (Summary)

Compartment

Key Nerve

Principal Actions

Key Features

Anterior

Femoral Nerve

Hip flexion, Knee extension

Contains Femoral Triangle

Medial

Obturator Nerve

Hip adduction, Hip flexion, Stabilization

Posture stabilizing muscles

Posterior

Sciatic Nerve

Hip extension, Knee flexion

Hamstring muscle group

Neurovasculature of the Lower Extremity

Arteries of the Hip and Thigh

The primary arterial supply to the hip and thigh region includes:

  • Femoral Artery: The main artery of the anterior thigh, continuing from the external iliac artery.

  • Deep Femoral Artery (Profunda Femoris): A large branch off the femoral artery, supplying most of the thigh muscles.

  • Medial Circumflex Artery: Important for the blood supply to the head of the femur, forming an anastomosis with the lateral circumflex femoral artery.

  • Lateral Circumflex Artery: Also contributes to the blood supply of the femoral head and surrounding muscles.

  • Superior Gluteal Artery: Supplies the gluteus medius, minimus, and tensor fasciae latae.

  • Inferior Gluteal Artery: Supplies the gluteus maximus and other deep gluteal muscles.

  • Collateral Circulation: Extensive anastomoses exist around the hip joint, providing alternative routes for blood supply, which is crucial in cases of arterial obstruction.

Veins of the Hip and Thigh

Venous drainage occurs from superficial to deep veins, with valves preventing backflow and the skeletal muscular pump aiding venous return.

  • Femoral Vein: The major deep vein of the thigh, accompanying the femoral artery.

  • Great Saphenous Vein: A large superficial vein that eventually drains into the femoral vein.

  • Superior Gluteal Vein: Drains blood from the superior gluteal region.

  • Inferior Gluteal Vein: Drains blood from the inferior gluteal region.

Nerves of the Lower Extremity

Key nerves innervating the lower extremity, especially in the hip and thigh, include:

  • Femoral Nerve: Primarily innervates the anterior compartment of the thigh.

  • Obturator Nerve: Primarily innervates the medial (adductor) compartment of the thigh.

  • Sciatic Nerve: The largest nerve in the body, innervating the posterior compartment of the thigh and all muscles below the knee.

  • Superior Gluteal Nerve: Innervates gluteus medius, gluteus minimus, and tensor fasciae latae.

  • Inferior Gluteal Nerve: Innervates gluteus maximus.