Bones of Lower Limb

Bones of the Lower Limb

• The distal part of the limb consists of the tibia and fibula, with the tibia being the largest and weight-bearing bone.
• The tibia articulates with the knee joint, while the fibula is excluded from the knee joint but participates in the ankle joint.
• The leg bones are held together by joints at both ends and by an interosseous membrane.
• The foot is held at right angles to the leg and contains tarsal bones, metatarsal bones, and phalanges.
• In standing, weight is transmitted from the ankle joint posteriorly via the tarsal bones to the heads of the metatarsals, forming an arch between the areas of contact with the ground.

Nerves of the Lower Limb

• There are six main nerves of the lower limb:
  • Superior gluteal nerve, which supplies the abductors of the hip.
  • Inferior gluteal nerve, which supplies the gluteus maximus muscle.
  • Femoral nerve, which supplies the anterior compartment of the thigh.
  • Obturator nerve, which supplies the medial compartment of the thigh.
  • Tibial nerve, which supplies the posterior muscles in the thigh and leg, and also supplies the muscles on the sole of the foot.
  • Common fibular (common peroneal) nerve, which divides into superficial and deep fibular nerves.

Compartments of the Thigh

• The thigh has three compartments: anterior, medial, and posterior.
• The anterior compartment contains the extensors of the knee joint.
• The medial compartment, also known as the adductor compartment, contains the adductor muscles of the hip.
• The posterior compartment contains the flexors of the knee.

Compartments of the Leg

• The leg has three compartments: anterior, posterior, and lateral.
• The posterior compartment contains the plantar flexors of the ankle and flexors of the toes.
• The anterior compartment contains the extensor muscles.
• The lateral compartment contains muscles that aid the posterior muscles in flexion of the ankle.

Capsule Attachments

• The capsule is strong due to the presence of thickenings of the capsule, called capsular ligaments.
• There are three ligaments: iliofemoral, pubofemoral, and ischiofemoral.
• These ligaments attach proximally to the acetabulum and distally to the intertrochanteric line.

Capsular Ligaments

• The iliofemoral ligament is the strongest ligament in the human body, with a tensile strength 20 times that of reinforced concrete.
• The iliofemoral ligament has a Y-shape and attaches to the iliac margins of the acetabular labrum and extends proximally towards the anterior inferior iliac spine.
• The pubofemoral ligament arises from the pubic margin of the acetabulum and inserts onto the lesser trochanter.
• The ischiofemoral ligament arises from the ischial margin of the acetabulum and inserts largely into the iliofemoral ligament, but also onto the greater trochanter.

Zona Orbicularis

• The zona orbicularis is a circular ligament that arises from the ischiofemoral ligament and serves to pinch the capsule around the neck of the femur.
• It aids in holding the femoral head into the acetabular socket, acting like a purse-string.

Blood Supply of the Femoral Head

• The blood supply to the joint is complex and involves five different arteries and two separate anastomoses.
• The head of the femur depends on its blood being delivered from distal to proximal, mainly through the medial circumflex femoral artery.
• Branches from the circumflex arteries run along the neck of the femur, dragging the capsule and synovium into folds, and then enter nutrient foraminae to reach the femoral head.
• If there is a fracture of the femur, these vessels may be at risk of rupture, leading to avascular necrosis of the femoral head.