8.4

Bones of the Lower Limb

Introduction to the Lower Limb

  • The lower limb is divided into three regions:

    • Thigh: Located between the hip joint and knee joint.

    • Leg: Located between the knee joint and ankle joint.

    • Foot: Located distal to the ankle.

  • The lower limb contains 30 bones, including:

    • Femur

    • Patella

    • Tibia

    • Fibula

    • Tarsal bones

    • Metatarsal bones

    • Phalanges

Femur

  • The femur is the single bone of the thigh region.

  • Characteristics:

    • Longest and strongest bone of the body, accounting for approximately one-quarter of a person’s total height.

    • Proximal end: Head of the femur, articulates with the acetabulum of the hip bone, forming the hip joint.

    • Fovea capitis: Minor indentation on the medial side of the femoral head, serves as the site of attachment for the ligamentum teres (ligament of the head of the femur), containing an important artery that supplies the head of the femur.

  • Articulations:

    • Superiorly: With the hip bone at the hip joint.

    • Inferiorly: With the tibia at the knee joint.

  • Key landmarks:

    • Neck of the femur: Common area for fractures.

    • Greater trochanter: Large bony projection providing leverage for muscles attaching at the hip joint.

    • Lesser trochanter: Small bony prominence on the medial aspect of the femur.

    • Intertrochanteric line: Roughened line between the greater and lesser trochanters on the anterior side.

    • Intertrochanteric crest: Connects the trochanters on the posterior side.

    • Linea aspera: Roughened ridge along the posterior mid-femur, for muscle attachment.

  • Distal end features:

    • Medial and lateral condyles covered with smooth surfaces for articulation with the tibia.

    • Epicondyles provide attachment for muscles and ligaments.

    • Intercondylar fossa: Deep depression separating the medial and lateral condyles.

    • Patellar surface: Anterior smooth surface for articulation with the patella.

Patella

  • The patella (kneecap) is the largest sesamoid bone in the body.

  • Definition: A sesamoid bone is incorporated into a tendon to protect it from damage during joint movements.

  • Found embedded within the tendon of the quadriceps femoris muscle.

  • Articulates with the patellar surface of the femur to lift the tendon away from the knee joint, increasing the leverage power of the quadriceps muscle.

  • Not articulated directly with the tibia.

Runner’s Knee (Patellofemoral Syndrome)

  • Most common overuse injury among runners, especially prevalent in adolescents and females.

  • Symptoms: Dull, aching pain around the front of the knee, aggravated by activities such as walking, running, kneeling, or prolonged sitting.

  • Causes: Variations in the shape and movement of the patella, direct trauma, or improper footwear leading to abnormal tracking of the patella.

  • The Q-angle is measured to assess the angle of femoral deviation from vertical:

    • Normal range: 10–15 degrees, larger in females due to wider pelvis.

    • Imbalances may lead to pain and potential arthritis.

Tibia

  • The tibia (shinbone) is the medial and larger bone of the leg, paired with the fibula.

  • Characteristics:

    • Main weight-bearing bone of the lower leg, second longest in the body after femur.

    • Medial side is easily palpated.

  • Proximal end features:

    • Medial condyle and lateral condyle smooth surfaces articulate with femur to form the knee joint.

    • Intercondylar eminence serves as attachment for knee ligaments.

    • Tibial tuberosity: Site for tendon attachment of the patella.

  • The shaft becomes triangular, with borders easily felt under the skin.

  • Medial malleolus at distal end, articulates with the talus bone at the ankle joint.

  • Lateral side features fibular notch, articulates with distal fibula.

Fibula

  • The fibula is the slender bone located on the lateral side of the leg.

  • Characteristics:

    • Does not bear weight, primarily serves for muscle attachments.

    • Proximal head articulates with the lateral tibial condyle, forming the proximal tibiofibular joint.

    • Distal end forms the lateral malleolus, easily palpated, and articulates with the talus at the ankle joint.

Tarsal Bones

  • The posterior half of the foot contains seven tarsal bones:

    • Talus: Square-shaped, articulates with tibia and fibula to form the ankle joint.

    • Calcaneus: Largest bone, forms the heel, and has a bony extension (sustentaculum tali) supporting the talus.

    • Cuboid: Articulates anteriorly with calcaneus.

    • Navicular: Articulates with talus and cuneiform bones.

    • Cuneiform bones: Medial, intermediate, and lateral cuneiforms.

Metatarsal Bones

  • Comprised of five metatarsal bones located between tarsal and phalangeal bones.

  • Numbered 1-5, starting from the medial side of the foot:

    • First metatarsal: Shorter and thicker.

    • Second metatarsal: Longest.

  • Bases articulate with tarsal bones and heads articulate with proximal phalanges at metatarsophalangeal joints.

Phalanges

  • The toes contain a total of 14 phalanx bones, organized similarly to the fingers.

  • Toes are numbered 1-5, starting with the big toe (hallux):

    • The big toe has 2 phalanx bones (proximal and distal).

    • Other toes have proximal, middle, and distal phalanges.

  • Interphalangeal joints connect adjacent phalanx bones.

Arches of the Foot

  • The foot's arches absorb impact and distribute body weight during movement:

    • Transverse arch: Formed by cuneiform bones and bases of metatarsal bones, enables accommodation of uneven terrain.

    • Longitudinal arches: Comprises medial (higher) and lateral (flatter) arches.

  • Functions of arches:

    • Flatten under body weight to absorb shock and rebound upon weight removal, storing energy.

    • Strong ligaments maintain arch integrity.

    • Condition such as pes planus (“flat foot” or “fallen arches”) can occur when the ligaments stretch too much, leading to pain and arch collapse.