Lab: Bones of the Lower Limb

Lab: Bones of the Lower Limb

Pelvic Bones

The sacrum consists of five fused sacral vertebrae; the coccyx of three to four fused coccygeal segments. The hip bone (os coxae) is formed by fusion of ilium, ischium, and pubis at the acetabulum. The greater (false) pelvis lies above the pelvic brim and contains abdominal organs; the lesser (true) pelvis lies below, forming the birth canal. Sex differences: female pelvis has a wider sub-pubic angle (>90° vs <90° in males), a larger oval inlet, a shallower cavity, and a wider outlet — adaptations for childbirth.

Femur

The femur is the longest bone. The obliquity angle (neck-shaft angle ~126°, greater in women due to wider pelvis) determines medial placement of the knee under the centre of mass. Important landmarks: head, neck (surgical vs anatomical neck), greater trochanter (gluteus medius/minimus insertion), lesser trochanter (iliopsoas insertion), linea aspera (many muscle attachments), medial and lateral condyles, intercondylar notch (cruciate ligament attachments), adductor tubercle (adductor magnus insertion).

Patella, Tibia, Fibula

The patella is a sesamoid bone within the quadriceps tendon — it increases the mechanical advantage of quadriceps by increasing the moment arm. Tibia: medial condyle, lateral condyle, tibial plateau, tibial tuberosity (patellar ligament attachment), medial malleolus. Fibula: lateral malleolus, fibular head (common fibular nerve wraps around here). The interosseous membrane between tibia and fibula transmits weight and provides muscle attachment.

Foot Bones

Tarsals: calcaneus (largest, sustentaculum tali supports talus head), talus (no muscles attach), navicular, cuboid, 3 cuneiforms. Metatarsals 1–5; phalanges (2 in hallux, 3 in each other toe). The base of the 5th metatarsal has a tuberosity where fibularis brevis inserts; avulsion fracture occurs with forced inversion.

Clinical Correlates

Neck of femur (NOF) fractures: common in elderly women with osteoporosis; intracapsular NOF fractures risk avascular necrosis of femoral head. March fracture: stress fracture of 2nd metatarsal shaft. Calcaneal spur: bony excrescence at calcaneal plantar aponeurosis attachment (related to plantar fasciitis). Prepatellar bursitis (housemaid's knee): repeated kneeling on hard surface. Superficial infrapatellar bursitis (clergyman's knee): kneeling more upright.