1.2 Femur

Introduction

• Femur is the longest and strongest bone in the human body. It forms the skeleton of the thigh. The plural of femur is femurs or femora (femur means thigh in Latin).
• The average length of the femur is about 45 cm (18 inches).

Parts of Femur

• The femur consists of three parts:
  1. Upper end
  2. Shaft (body)
  3. Lower end
• Upper End: The upper end includes: Head, neck, greater trochanter, and lesser trochanter
• Shaft: The shaft is long and cylindrical in shape.
• Lower End: The lower end is broad and expanded. It has: Medial epicondyle, lateral epicondyle, medial condyle, and lateral condyle
• The intercondylar fossa separates the two condyles.

Anatomical Position and Side Determination

Hold the femur vertically so that:

• The head faces upward, medially, and slightly forward.
• The smooth convex anterior surface of the shaft faces forward.
• The shaft slopes downward and medially, allowing both condyles to rest in the same horizontal plane.

Features of Femur

• The femur has an upper end, a middle shaft, and a lower end.

Upper End of Femur

The upper end of the femur consists of:

1. Head
2. Neck
3. Greater trochanter
4. Lesser trochanter

Head

• The head is globular and forms about two-thirds of a sphere.
• It is directed upward, medially, and slightly forward.
• Most of its surface is covered by hyaline cartilage, except at the fovea.

Fovea Capitis Femoris

• The fovea capitis femoris is a small depression near the center of the head.
• It provides attachment for the ligament of the head of the femur (ligamentum teres femoris).

Articulation

• The head of the femur articulates with the acetabulum of the hip bone.
• Together, they form the hip joint, which is a ball-and-socket synovial joint.

Neck of femur

• The neck is the narrow part that connects the head to the shaft.
• The average length of the neck is about 5 cm.
• The neck has:
  • Two borders: Upper and lower
  • Two surfaces: Anterior and posterior
• Upper Border: The upper border is short, concave, and horizontal.
• Lower Border: The lower border is longer, straight, and oblique.
• Anterior Surface: The anterior surface is flat. Extension occurs from the head to the intertrochanteric line. The entire anterior surface is intracapsular.
• Posterior Surface: The posterior surface is convex from above downward and concave from side to side. Extension occurs from the head to the intertrochanteric crest. The medial half of the posterior surface is intracapsular.
• Intertrochanteric Line: The intertrochanteric line marks the anterior junction of the neck and shaft. Its course is downward and medially from the greater trochanter to the lesser trochanter.

Attachments

1. Capsule of the hip joint
2. Iliofemoral ligament
3. Vastus lateralis (upper part)
4. Vastus medialis (lower part)

• Intertrochanteric Crest: The intertrochanteric crest is a broad, prominent ridge on the posterior aspect of the femur. Its location is at the junction of the neck and shaft. Its extent is from the greater trochanter to the lesser trochanter. Its prominence is greater than that of the intertrochanteric line.

• Quadrate Tubercle: The quadrate tubercle is a rounded elevation near the middle of the intertrochanteric crest. Insertion of the quadratus femoris muscle occurs on the quadrate tubercle.

Blood supply of head of femur

• The blood supply of the head of the femur is of great surgical importance.
• The retinacular arteries, mainly arising from the medial circumflex femoral artery, provide the major blood supply to the femoral head.

Sources of Arterial Supply

1. Extracapsular Arterial Ring

• The extracapsular arterial ring is located at the base of the femoral neck.
• Its formation includes:
  • A large posterior branch of the medial circumflex femoral artery.
  • A small anterior branch of the lateral circumflex femoral artery.

2. Ascending Cervical (Retinacular) Arteries

• The ascending cervical (retinacular) arteries arise from the extracapsular arterial ring.
• Their course is along the femoral neck beneath the capsule.
• These retinacular arteries supply most of the head of the femur.

3. Artery of the Ligament of the Head of the Femur

• The artery of the ligament of the head of the femur (ligamentum teres) usually arises from the obturator artery.
• An occasional origin is from the medial circumflex femoral artery.
• Its blood supply is insufficient to maintain the femoral head on its own.

Clinical Correlation: Avascular Necrosis

• A displaced fracture of the femoral neck can damage the retinacular arteries.
• Loss of the retinacular blood supply may lead to avascular necrosis of the head of the femur.
• The artery of the ligamentum teres alone cannot adequately supply the femoral head after such an injury.

Greater trochanter

• The greater trochanter is a large quadrangular projection at the junction of the neck and shaft of the femur.
• It has:
  • One border: Upper border
  • Three surfaces: Anterior, medial, and lateral
• Upper Border: The upper border bears the apex (tip).
  • Attachment: Piriformis inserts at the apex of the greater trochanter.
• Anterior Surface: The anterior surface is rough laterally.
  • Attachment: Gluteus minimus inserts on the rough lateral part of the anterior surface.
• Medial Surface: The medial surface contains two depressions.
• Trochanteric Fossa: The trochanteric fossa is a deep depression on the lower part of the medial surface.
  • Attachment: Obturator externus inserts into the trochanteric fossa.
• Upper Depression: The upper depression is smaller and less prominent.
  • Attachment: Obturator internus and the superior and inferior gemelli insert into the upper depression.
• Lateral Surface: The lateral surface is quadrilateral. An oblique ridge divides it into upper and lower triangular areas. The oblique ridge runs downward and forward.
  • Attachment: Gluteus medius inserts on the oblique ridge of the lateral surface.

Lesser trochanter

• The lesser trochanter is a prominent conical bony projection at the inferomedial aspect of the neck-shaft junction.

Attachments

• The apex of the lesser trochanter provides insertion for the psoas major muscle.
• The lower part of the lesser trochanter and the adjacent area of the shaft provide insertion for the iliacus muscle.

Shaft of Femur

• The shaft of the femur is cylindrical and narrowest in the middle. The shaft inclines medially in the anatomical position. The shaft has:
  • Five surfaces: Anterior, medial, lateral, posterior, and popliteal
  • Three borders: Medial, lateral, and posterior

Borders of shaft

• The medial border is rounded and ill-defined.
• The lateral border is rounded and ill-defined.
• The posterior border is represented by the linea aspera.

Surfaces of shaft

• The middle one-third has three surfaces:
  • Anterior
  • Medial
  • Lateral
• The upper part has a triangular posterior surface between the two lips of the linea aspera.
• The lower one-third has the popliteal surface, located between the medial and lateral supracondylar lines.

Attachments

• The upper three-fourths of the anterior surface and the adjacent lateral surface provide origin for the vastus intermedius.
• The anterior surface, just below the origin of the vastus intermedius, provides origin for the articularis genu.
• The line extending from the lesser trochanter to the upper part of the linea aspera provides insertion for the pectineus.
• The gluteal tuberosity provides insertion for the deep fibers of the gluteus maximus.
• The popliteal surface and the adjacent medial condyle provide origin for the medial head of the gastrocnemius.

Linea aspera

• The linea aspera (Latin: rough line) is a thick rough ridge along the middle of the posterior border of the femoral shaft.
• It consists of:
  • Medial lip
  • Intermediate area
  • Lateral lip

Upper Part

• The medial and lateral lips diverge in the upper part of the shaft. A triangular posterior surface lies between the two lips. The medial lip continues as the spiral line. The lateral lip continues as the gluteal tuberosity (third trochanter).

Lower Part

• The medial and lateral lips diverge in the lower part of the shaft. A triangular popliteal surface lies between the two lips. The medial lip continues as the medial supracondylar line. The lateral lip continues as the lateral supracondylar line.

Development

• The linea aspera develops due to muscular pull.

Attachments

1. The lower part of the intertrochanteric line, spiral line, medial lip of the linea aspera, and upper one-fourth of the medial supracondylar line provide origin for the vastus medialis.
2. The medial lip provides attachment for the medial intermuscular septum.
3. The medial lip provides insertion for the adductor longus.
4. The line extending from the lesser trochanter to the upper part of the linea aspera provides insertion for the adductor brevis.
5. The medial margin of the gluteal tuberosity, linea aspera, medial supracondylar line, and adductor tubercle provide insertion for the adductor magnus.
6. The posterior aspect of the linea aspera provides attachment for the posterior intermuscular septum.
7. The lateral lip, between the lateral and posterior intermuscular septa, provides origin for the short head of the biceps femoris.
8. The upper part of the intertrochanteric line, inferior border of the greater trochanter, lateral margin of the gluteal tuberosity, and lateral lip of the linea aspera provide origin for the vastus lateralis.
9. The lateral lip provides attachment for the lateral intermuscular septum.

Lower End of Femur

• The lower end of the femur is broad and expanded.
• It consists of:
  • Medial condyle
  • Lateral condyle
  • Intercondylar fossa (intercondylar notch)

Medial condyle

• The medial condyle is larger and more prominent than the lateral condyle.
• The medial condyle projects lower than the lateral condyle, helping to compensate for the medial inclination of the femoral shaft.

Medial Epicondyle

• The medial epicondyle is the most prominent point on the medial condyle.
• Attachment: The tibial (medial) collateral ligament attaches to the medial epicondyle.

Adductor Tubercle

• The adductor tubercle lies posterosuperior to the medial epicondyle at the lower end of the medial supracondylar line. Its appearance may be as a small tubercle or a facet.
• Attachment: The ischial (hamstring) part of the adductor magnus inserts on the adductor tubercle.

Lateral condyle

• The lateral condyle is longer anteroposteriorly, stouter, and stronger than the medial condyle.

Lateral Epicondyle

• The lateral epicondyle is a low rounded elevation on the lateral aspect of the lateral condyle.
• Attachment: The fibular (lateral) collateral ligament attaches to the lateral epicondyle.

Popliteal Groove

• The popliteal groove lies just below the lateral epicondyle. The groove has:
  • Anterior deep part
  • Posterior shallow part
• Attachments: The anterior deep part provides origin for the popliteus muscle. The posterior shallow part accommodates the tendon of the popliteus during knee flexion.

Muscular Impression

• The muscular impression lies posterosuperior to the lateral epicondyle. The lateral head of the gastrocnemius originates from the muscular impression.

Intercondylar fossa (intercondylar notch)

• The intercondylar fossa is a deep notch between the medial and lateral condyles on the posterior aspect of the femur.
• It has:
  • Medial wall
  • Lateral wall
  • Floor
• The intercondylar line separates it from the popliteal surface posteriorly.
• The lower border of the patellar articular surface forms its anterior limit.
• Attachments
  1. The posterior part of the medial surface of the lateral condyle provides attachment for the anterior cruciate ligament (ACL).
  2. The anterior part of the lateral surface of the medial condyle provides attachment for the posterior cruciate ligament (PCL).
  3. The intercondylar line provides attachment for the capsule of the knee joint.
  4. The lateral part of the intercondylar line provides attachment for the oblique popliteal ligament.

Articular surface

• The articular surface at the lower end of the femur is V-shaped. The entire articular surface is covered by hyaline cartilage. The articular surface has two parts:
  • Patellar articular surface
  • Tibial articular surface

Patellar Articular Surface

• The patellar articular surface covers the anterior surfaces of both condyles. Its extent is greater on the lateral condyle than on the medial condyle. Two faint grooves separate it from the tibial articular surface.

Tibial Articular Surface

• The tibial articular surface covers the inferior and posterior surfaces of both condyles. The intercondylar notch separates the tibial articular surfaces of the two condyles.

Articulations

• The patellar articular surface articulates with the patella. The tibial articular surface articulates with the medial and lateral condyles of the tibia and the menisci to form the knee joint.

Ossification of Femur

• The femur ossifies from one primary center and four secondary centers.

Primary Ossification Center:

• The shaft develops from one primary ossification center. Its appearance occurs during the 7th–8th week of intrauterine life.

Secondary Ossification Centers

• Lower End: One secondary center appears for the lower end. Its appearance occurs during the 9th month of intrauterine life.
• Upper End: One secondary center appears for the head in the 1st year. One secondary center appears for the greater trochanter in the 4th year. One secondary center appears for the lesser trochanter during the 12th–14th years.

Fusion

• The upper end fuses with the shaft by about the 18th year. The lower end fuses with the shaft by about the 20th year.

Patella

• The patella is the largest sesamoid bone in the human body. The patella develops within the tendon of the quadriceps femoris muscle. Its shape is small, flat, and triangular. The patella is also known as the kneecap because of its position in front of the knee joint.

Parts

• Patella is a flat triangular bone. It has apex, base, and medial and lateral borders. It has rough convex anterior surface and large articular posterior surface.

Anatomical Position and Side Determination

• The apex faces downward.
• The rough convex anterior surface faces forward.
• The larger articular facet on the posterior surface lies on the same side as the bone.
• The right patella has the larger articular facet on the right side.
• The left patella has the larger articular facet on the left side.

Features of Patella

• The patella is a triangular bone. It has:
  • Apex
  • Three borders: Superior (base), medial, and lateral
  • Two surfaces: Anterior and posterior

Apex of patella

• The apex is directed downward.
• Attachment: The ligamentum patellae (patellar ligament) attaches to the apex of the patella.

Borders of patella

Superior Border (Base)

• The superior border (base) is rough and convex anteriorly.
• Attachments: The anterior part provides insertion for the rectus femoris. The posterior part provides insertion for the vastus intermedius.

Lateral Border

• The upper one-third provides attachment for the vastus lateralis. The lower two-thirds provide attachment for the lateral patellar retinaculum.

Medial Border

• The upper two-thirds provide attachment for the vastus medialis. The lower one-third provides attachment for the medial patellar retinaculum.

Surfaces of patella

The patella has two surfaces:

• Anterior surface
• Posterior surface

Anterior Surface

• The anterior surface is rough, non-articular, and convex. Numerous vascular foramina are present on this surface. The subcutaneous prepatellar bursa lies between the anterior surface and the skin.

Posterior Surface

• The posterior surface is divided into:
  • Upper three-fourths: Articular part
  • Lower one-fourth: Non-articular part

Articular Part

• The articular part is divided by a vertical ridge into:
  • Larger lateral articular area
  • Smaller medial articular area
• The smaller medial articular area is further divided by a small vertical ridge into:
  • Narrow medial strip
  • Larger lateral part
• The articular surface, except the narrow medial strip, is divided into upper, middle, and lower areas by two horizontal lines.

Articular Contact with the Femur

• The upper area comes in contact with the femur during mid-flexion. The middle area comes in contact with the femur during semi-flexion. The lower area comes in contact with the femur during extension. The narrow medial strip comes in contact with the medial surface of the intercondylar notch of the femur during full flexion.

Non-Articular Part

• The lower part provides attachment for the ligamentum patellae (patellar ligament). The upper part is related to the infrapatellar fat pad.

Ossification of Patella

• The patella ossifies within the tendon of the quadriceps femoris.
• Multiple ossification centers appear between 3 and 6 years of age.
• Fusion of these ossification centers occurs by puberty.

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