Lower Extremity, Posterior

Lower Extremity, Posterior

Sections

Origins & Insertions: Lower Extremity, Posterior

Origins & Insertions: Lower Extremity, Posterior

Origin

• The bone that remains stable upon muscle contraction.

Insertion

• The bone moves upon muscle contraction.

In the limbs, the origin is usually proximal to the insertion.

• Review key skeletal components:
  Pelvis
  Femur
  Leg & Foot

Ilium

• Origins of muscles that act on the hip:
  Gluteus maximus, medius, and minimus arise from the posterior pelvis and the gluteal lines.
  Tensor fasciae latae arises from the iliac crest and the lateral surface of the anterior superior iliac spine (ASIS) and merges with the iliotibial tract.
  Sartorius arises inferior to the tensor fasciae latae on the ASIS.
  Rectus femoris has two points of origin: superiorly, from anterior inferior iliac spine (AIIS) and, inferiorly, from the superior margin of the acetabulum.
  Superior gemellus arises from the ischial spine, and
  Inferior gemellus arises from the ischial tuberosity.
  Quadratus femoris arises from the inferior margin of the acetabulum.
  Semimembranosus arises just inferior to quadratus femoris on the ischial tuberosity.
  The long head of biceps femoris and semitendinosus arise together from the ischial tuberosity.
  Adductor magnus arises from the inferior ischiopubic ramus and ischial tuberosity.
  Obturator internus arises from the ischiopubic rami and the obturator membrane on the inner margin of the obturator foramen.

• Insertions of muscles that act at the hip:
  Obturator externus inserts in the trochanteric fossa of the posterior femur.
  Gluteus medius inserts on the greater trochanter.
  Quadratus femoris inserts at the intertrochanteric crest, and
  Iliopsoas inserts at the lesser trochanter.
  Gluteus maximus inserts along the gluteal tuberosity (and to the superior portion of the iliotibial tract).
  Adductor magnus inserts along the linea aspera and also on the adductor tubercle.
  Adductor brevis inserts along the pectineal line and the proximal portion of the linea aspera.
  Adductor longus inserts along the middle third of the linea aspera.
  Pectineus inserts at the pectineal line.

Femur

• Origins of muscles that act on the knee:
  Vastus lateralis arises from the greater trochanter, gluteal tuberosity, and lateral lip of the linea aspera (and lateral intermuscular septum).
  Vastus intermedius arises from the posterolateral shaft of the femur (and distal lateral intermuscular septum).
  The short head of biceps femoris arises from the lateral lip of the linea aspera.
  Vastus medialis arises from the medial lip of the linea aspera (and the intertrochanteric line and medial intermuscular septum).
  Plantaris, which arises from the lateral supracondylar line.
  Medial and lateral heads of gastrocnemius arise from the medial and lateral femoral condyles (some texts describe these origins as being on the epicondyles).
  Popliteus arises from the lateral condyle inferior to the lateral head of gastrocnemius.

• Insertions of muscles that act on the knee:
  Semimembranosus inserts on the medial condyle of the tibia.
  Popliteus inserts inferior to semimembranosus.

Tibia, Fibula, and Foot

• Origins of muscles that plantar flex the ankle and foot:
  Soleus arises separately from the head of fibula and the soleal line of the proximal tibia.
  Tibialis posterior arises from the interosseous membrane as well as the tibia and fibula.
  Flexor hallucis longus on the lateral fibula and the interosseous membrane (and the intermuscular septum).
  Fibularis brevis on the distal fibula (and intermuscular septum).
  Flexor digitorum longus arises on the mid-tibial shaft.

• Insertions of muscles that plantar flex the ankle and foot.
  Plantaris inserts on the posterior calcaneus.
  Calcaneal tendon (aka triceps surae, aka Achilles tendon), which is comprised of tendons from gastrocnemius and soleus, inserts on the calcaneus.
  Tibialis posterior has 7 insertion sites of tibialis posterior: on the tuberosity of the navicular, the three cuneiforms, and bases of metatarsals II-IV (some texts include the cuboid in this list).
  Tibialis anterior inserts on the medial aspects of the first cuneiform and first metatarsal of digit 1.
  Fibularis longus inserts on the lateral aspects of the first cuneiform and first metatarsal.
  Flexor hallucis longus inserts at the base of the distal phalanx of digit 1.
  Flexor digitiorum longus at the bases of the distal phalanges of toes 2-4.