Lower Limb Anatomy

• The lecture discusses the skeleton of the lower limb.
• The lower limb skeleton consists of 30 bones and is adapted for weightbearing.
• The lower limb includes the pelvic girdle, thigh, leg, and foot.

Appendicular Skeleton - Lower Limb

• The pelvic girdle comprises 2 hip bones and the sacrum. The sacrum is part of the axial skeleton.
• The femur (thigh bone), patella (knee cap), tibia (shin bone of leg), and fibula (calf bone of leg) are components of the lower limb.
• Included in the lower limb are the tarsals (ankle), metatarsals (foot), and phalanges (digits/toes).
• The number of each of these follows:
  • Femur = [2]
  • Patella = [1]
  • Tibia = [2]
  • Fibula = [2]
  • Tarsals = [7] x 2
  • Metatarsals = [5] x 2
  • Phalanges = [14] x 2
• The lower limb is adapted for weight-bearing, locomotion, and bipedal posture.

Pelvic Girdle

• The pelvic girdle consists of 2 hip bones (coxae), the sacrum, and the coccyx, forming the pelvis.
• Each hip bone consists of 3 fused bones: ilium, pubis, and ischium.
• Posteriorly, the hip bones articulate with the sacrum.
• Anteriorly, the hip bones articulate with the symphysis via cartilage.

Pelvic Girdle - Functions

• Functions of the pelvic girdle include supporting and protecting abdominal and pelvic organs and housing a developing fetus.
• It attaches the lower limbs to the trunk.
• Also transmits weight from the upper body and vertebral column to the lower limbs.

Hip Bones - Acetabulum (hip socket)

• The ilium, ischium, and pubis meet inside the acetabulum on the lateral surface of the hip bone.
• The acetabulum is described as a shallow, concave (cup-shaped) socket.
• It articulates with the head of the femur to form the hip joint.

Ilium

• The ilium constitutes the superior, fan-shaped part of the hip bone.
• Margins of the ilium include:
  • 4 spines (ASIS, AIIS, PSIS, PIIS).
  • 3 lines (anterior, posterior, and inferior gluteal lines).
  • 1 crest (iliac crest).
  • 1 notch (greater sciatic notch).
• The gluteal refers to the gluteus muscle attachment area.
• Spine refers to a pointed process similar to, but more raised than, a crest.
• Notch refers to a "V"-like cut.
• The broadest part of the ilium extends between the arcuate line and the iliac crest.
• Additional features include:
  • Iliac fossa.
  • Iliac tuberosity.
  • Auricular surface.
  • Arcuate line.

Ischium

• The ischium provides a broad base to bear weight when sitting.
• Components are:
  • Ischial ramus.
  • Ischial spine.
  • Ischial tuberosity.
  • Lesser sciatic notch.
• Spine refers to sharp, pointed process.
• Ramus refers to "branch".

Pubis

• The pubis includes 2 rami: inferior and superior pubic ramus.
• Features include:
  • Pubic tubercle.
  • Obturator foramen.
  • Pubic symphysis.
• Foramen refers to a rounded hole for blood vessels and nerves.
• The obturator foramen represents a large oval opening in the hip bone bounded by the pubis and ischium rami, closed by the obturator membrane.
• The obturator canal allows passage for the obturator nerve and vessels.

Checkpoint - Anatomical Position of the Hip Bone

• To determine the anatomical position of the hip bone, note that the ASIS (anterior superior iliac spine) and anterosuperior aspect of the pubis (pubic tubercle) lie in the same coronal plane.
• The symphysial surface of the pubis is vertical and parallel to the median plane.
• Consider the ischial spine and the upper part of the pubic symphysis which lie on the same horizontal plane.
• Understand that the acetabulum faces inferolaterally, with the acetabular notch directed inferiorly, and the obturator foramen lies inferomedially to it.

Pelvis

• The pelvis resembles a bony ring or basin interposed between the vertebral column and lower limbs.
• It is divided into true and false pelvis by the pelvic brim.
• The false (greater) pelvis is the expanded portion of the cavity above the pelvic brim that supports abdominal organs.
• The true (lesser) pelvis is inferior to the pelvic brim and consists of an inlet, outlet, and cavity, containing the pelvic organs.

Male and Female Pelvis

• Male and female pelves differ in many aspects.
• The female pelvis is smoother and lighter with fewer muscle attachments and has beenmodified for childbearing, with:
  • An enlarged pelvic outlet.
  • A broad pubic angle (>100°).
  • Less curvature of sacrum and coccyx.
  • A wide, circular pelvic inlet.
  • A broad, low pelvis.
  • With ilia projecting laterally rather than upwards.

Femur

• The femur is the bone of the thigh and the longest, heaviest bone in the body.
• It articulates with the hip bone at the hip joint and with the tibia at the knee joint.
• In an erect posture, it inclines slightly medially.
• The proximal end includes the head, neck, greater and lesser trochanters, intertrochanteric line, and crest.
• The shaft includes the linea aspera, gluteal tuberosity, and popliteal surface.
• The distal end features lateral and medial epicondyles, lateral and medial condyles, and patella surface.

Femur - Proximal End

• The femoral head articulates with the pelvis at the acetabulum and attaches with a ligament at the fovea capitis (small pit in the head's center).
• The neck joins the femur head and shaft.
• Included are the Greater & Lesser trochanters which consist of large, rough projections at the junction of the neck and shaft for tendon attachments.
• The intertrochanteric line marks the articular capsule's edge is the location the intertrochanteric crest forms posteriorly.

Femur - Shaft

• The middle third of the shaft is triangular in shape.
• The posterior margin is broad, forming the linea aspera. This area includes:
  • A ridge that runs along the center of the posterior surface.
  • An attachment area for hip muscles.
• Medial & lateral margins continue superiorly as the pectineal line and gluteal tuberosity and inferiorly as the medial & lateral supracondular ridges.
• The popliteal surface is located most distally between the ridges.
• Trochanter refers to a very large bump (larger than a tuberosity and tubercle), and crest is used when referring moderately raised areas.

Femur - Distal End

• Medial and lateral epicondyles are projections above the knee joint.
• Medial and lateral condyles are rounded surfaces that form part of the knee joint. They are:
  • Separated by the intercondylar fossa posteriorly.
  • Separated by the patellar surface anteriorly and inferiorly.
• The adductor tubercle is a small prominence above the medial epicondyle for muscle attachment.

Femur - Fractures

• Despite its size and strength, the femur is commonly fractured, especially at the neck which is the narrowest and weakest point.
• It is due to a marked angle to the line of weight-bearing.
• This area becomes vulnerable with age, especially in females, secondary to osteoporosis.
• Fractures to the femoral shaft usually result from direct trauma (direct blows sustained by the bone resulting from falls or being hit).
• These are the areas often damaged and are most common during the more active years due to motor vehicle accidents and sports.

Checkpoint - Anatomical Position of the Femur

• To determine the anatomical position of the femur (thigh bone), locate the femoral head, which articulates medially with the acetabulum of the hip bone. Then, determine which side is anterior or posterior either by finding the patellar surface (anterior) or the intercondylar fossa (posterior).

Patella (kneecap)

• This is a flat triangular, sesamoid bone situated anterior to the distal end of the femur.
• Surfaces:
  • Anterior surface: roughened.
  • Posterior surface: smooth and oval, with medial and lateral facets articulating with condyles of femur.
• Borders: -Includes a base (superior border) and medial and lateral borders.
• Has an Apex: pointed inferiorly.
• Its functions include:
  • Protecting the tendon against friction.
  • Changing the direction of pull.
  • Increasing mechanical advantage.

Overview of the lower limb skeleton, which includes the pelvic girdle, thigh, leg, and foot. Adapted for weight-bearing, locomotion, and bipedal posture, the lower limb consists of 30 bones. Key components include the femur, patella, tibia, fibula, tarsals, metatarsals and phalanges.