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Femur

Medically Reviewed by Anatomy Team

  • Last updated on January 28, 2025

Table of Contents

The femur, also known as the thigh bone, is the longest, strongest, and heaviest bone in the human body.[6] It forms the upper part of the leg and plays a crucial role in supporting body weight and enabling locomotion. The femur is a typical long bone, consisting of a head, neck, shaft, and distal end. Its robust structure allows it to withstand significant forces during activities such as walking, running, and jumping.

Location

The femur is located in the thigh region, extending from the hip to the knee.[4] Proximally, it articulates with the hip bone at the acetabulum, forming the hip joint. Distally, it connects with the tibia and patella to form the knee joint.

Structure and Anatomy

The femur is a long bone comprising three main parts: the proximal end, the shaft, and the distal end. Its design allows for both weight-bearing and movement.

Proximal End

Head of the Femur

  • Shape and Position: Spherical in shape and forms the proximal-most part of the femur.
  • Articulations: Fits into the acetabulum of the hip bone to form the hip joint.
  • Notable Features:
    • The fovea capitis: A small depression on the head where the ligament of the head of the femur attaches.

Neck of the Femur

  • Shape and Orientation: Cylindrical and connects the head to the shaft, angling medially to facilitate weight transfer.
  • Angle of Inclination: Typically around 125 degrees, varying with age and sex.
  • Significance: Prone to fractures due to its thinner structure.

Greater Trochanter

  • Position: Lateral and superior to the femoral shaft.
  • Attachments: Serves as a site for the attachment of muscles like gluteus medius, gluteus minimus, and piriformis.[1]

Lesser Trochanter

  • Position: Posteromedial aspect of the femur, below the neck.
  • Attachments: Provides attachment for the iliopsoas muscle.

Intertrochanteric Line and Crest

  • Line: Located anteriorly, connecting the greater and lesser trochanters.
  • Crest: Found posteriorly and more prominent, also connecting the two trochanters.

Shaft

Shape and Orientation

  • Shape: The shaft is slightly bowed anteriorly, allowing it to handle compressive forces effectively.
  • Three Borders: Medial, lateral, and posterior borders define the shaft.
  • Three Surfaces: Anterior, medial, and lateral surfaces are relatively smooth.

Linea Aspera

  • Position: A prominent ridge running longitudinally on the posterior surface of the shaft.
  • Attachments: Serves as an attachment site for muscles such as the adductor longus, vastus medialis, and vastus lateralis.[8]
  • Split: Distally, it divides into medial and lateral supracondylar lines.

Nutrient Foramen

  • Found on the posterior aspect, providing an entry point for the nutrient artery.

Distal End

Medial and Lateral Condyles

  • Shape: Rounded and prominent structures at the distal end.[7]
  • Articulations: These condyles articulate with the tibia and patella to form the knee joint.
  • Notable Features: The medial condyle is larger and slightly more prominent than the lateral one.

Intercondylar Fossa

  • Position: A deep notch between the two condyles on the posterior side.
  • Significance: Provides space for the attachment of the cruciate ligaments of the knee.

Medial and Lateral Epicondyles

  • Position: Located above the condyles, serving as attachment points for ligaments.

Patellar Surface

  • Position: Anteriorly located, a smooth groove where the patella articulates.

Vascular Supply

  • Nutrient Artery: Enters through the nutrient foramen on the posterior shaft.
  • Proximal Supply: Provided by branches of the medial and lateral circumflex femoral arteries.
  • Distal Supply: Supplied by branches of the popliteal artery.

Notable Features

  • The femur is the largest and strongest bone, capable of supporting substantial forces.
  • It is richly vascularized, with several muscle and ligament attachments ensuring stability and mobility.
  • Its shape and orientation adapt over time to weight-bearing stresses and locomotion.[5]

Function

  • Support and Weight-Bearing
    The femur is the primary weight-bearing bone of the body. It transmits forces from the hip to the knee, supporting the body during standing, walking, and running.
  • Locomotion and Movement
    The femur facilitates movement by serving as a lever for muscles acting on the hip and knee joints. Its articulations at the hip and knee allow for a wide range of motions, including flexion, extension, abduction, adduction, and rotation.
  • Formation of Joints
    • Hip Joint: The femoral head forms a ball-and-socket joint with the acetabulum, enabling multi-directional movement.
    • Knee Joint: The distal femur forms a hinge joint with the tibia and patella, allowing flexion and extension of the leg.
  • Attachment Site for Muscles and Ligaments
    The femur provides multiple attachment points for muscles and ligaments of the lower limb, including the quadriceps, hamstrings, gluteals, and adductors.[3] These attachments are critical for stability and movement.
  • Protection of Bone Marrow
    The femur encloses bone marrow in its medullary cavity, which plays a role in hematopoiesis (production of blood cells).
  • Shock Absorption
    Its robust structure and slight curvature allow it to absorb and distribute mechanical stress during activities such as running or jumping.

Clinical Significance

The femur is of great clinical importance due to its central role in weight-bearing, movement, and its susceptibility to injuries and conditions:

  • Fractures:
    • Femoral Neck Fractures: Common in the elderly, especially those with osteoporosis, often leading to hip replacements.
    • Shaft Fractures: Typically result from high-energy trauma, such as motor vehicle accidents.
    • Distal Femur Fractures: May involve the knee joint and require surgical intervention.
  • Hip Disorders:
    • Conditions like developmental dysplasia of the hip (DDH) and slipped capital femoral epiphysis (SCFE) affect the femoral head and its articulation with the acetabulum.
  • Osteoarthritis:
    • Degenerative changes in the hip or knee joint involving the femoral articulations can lead to pain, stiffness, and reduced mobility.[2]
  • Femoral Artery Compromise:
    • Injuries to the femur can damage the nearby femoral artery, leading to significant blood loss and vascular complications.
  • Bone Tumors:
    • Primary or metastatic bone cancers, such as osteosarcoma, often involve the femur.
  • Femoral Length Discrepancy:
    • Trauma or congenital conditions can result in a difference in femoral length, affecting gait and posture.