Musculoskeletal: Anatomy - Development of lower limb

Question 1

Six major regions of the lower limb and boundaries

Answer 1

1. Gluteal: superior border iliac crest, medial border intergluteal cleft
2. Femoral: separated from gluteal region by gluteal fold, inguinal ligament and ischiopubic ramus
3. Knee: includes distal femoral condyles and proximal tibial condyles, head of fibula, patella, and their joints
4. Leg: between knee and ankle
5. Talocrural (ankle): medial and lateral malleoli
6. Foot: tarsus, metatarsus, and phalanges

Question 2

When do lower limb buds emerge? Where do they emerge from?

Answer 2

5th week of development
From lateral aspect L2-S2 segments of trunk

Question 3

What is the initial orientation of the lower limb buds and how does this change? Describe the timing of these changes

Answer 3

Lower limb buds appear at 5th week of development and grow laterally from the L2-S2 segments
Initially extend from trunk with great toes directed superiorly and soles of feet anteriorly
Flexures develop between the precursors of the long bones and the limbs bend anteriorly, such that the knee is directed laterally and the sole of the foot medially
By the end of the 7th week, proximal lower limb undergoes 90° torsion around its long axis such that the knee is directed cranially (upper limb also torts 90° but in the opposite direction, such that the elbow is directed caudally)
Torsion is accompanied by permanent pronation of leg such that foot becomes oriented with great toe on the medial side

Torsion and twisting of lower limb is still ongoing at birth, and completion coincides with mastering of walking