Origins & Insertions - Lower Extremity, Anterior

• We'll be looking at the right side.

• The bone that remains stable upon muscle contraction.

• 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

• Origin sites on the ilium:

Iliacus arises from the iliac fossa and joins with fibers from psoas major (a muscle that originates from the axial skeleton) to form iliopsoas. Sartorius arises from the anterior superior iliac spine (ASIS). Rectus femoris arises from the anterior inferior iliac spine (AIIS) and the posterior-superior edge of the acetabulum. Piriformis arises from the anterior surface of the sacrum (and sacrotuberous ligament).

• Origin sites on the medial pelvis and margins of the obturator foramen:

Pectineus arises from the pectineal line of the pubis. Adductor longus arises from the body of the pubis inferior to the pubic crest. Adductor brevis and gracilis arise from the pubic body and inferior pubic ramus. Adductor magnus arises from the ischiopubic ramus and ischial tuberosity. Quadratus femoris arises from the ischial tuberosity. Obturator externus arises from the inner margin of the obturator foramen (and the obturator membrane).

• Insertions of muscles that act on the hip:

Collective tendinous insertion of obturator internus, superior gemellus, and inferior gemellus on the medial aspect of the greater trochanter. Piriformis inserts on the superior portion of the greater trochanter anterior to this collective tendinous insertion. Gluteus minimum inserts on the lateral aspect of the greater trochanter. Iliopsoas, which comprises fibers from iliacus and psoas major, inserts on the lesser trochanter. Adductor magnus inserts at the medial supracondylar line and adductor tubercle (and posteriorly on the linea aspera).

• Muscles that arise on the femur and extend the knee:

Quadriceps femoris Vastus lateralis arises from the lateral aspect of the intertrochanteric line and inferior portion of the greater trochanter (it also arises from the posterior aspect of the femur). Vastus intermedius arises from the anterolateral aspect of the femur; it covers most of the anterior surface of the femur. Vastus medialis arises from the medial aspect of the intertertrochanteric line (it also arises from the posterior aspect of the femur). Notably, these three vastus muscles insert at the patellar tendon with rectus femoris to create the quadriceps femoris. Articularis genus arises superior to the patellar surface of the distal femur (genu = knee).

• Insertions sites of muscles on the tibia and fibula of the leg:

Proximal tibia, from lateral to medial: Iliotibial tract, which partially encloses the tensor fasciae latae muscle superiorly, inserts at the lateral aspect of the condyle of the tibia. Quadriceps femoris (aka collective tendon of the vastus medialis, intermedius, and lateralis) inserts via the patellar ligament on the tibial tuberosity. Sartorius, gracilis, and semitendinosus insert on the medial aspect of the superior tibia. Together, these tendons are referred to as the pes anserinus ("goose's foot"). Fibular head: Biceps femoris.

• Origins of muscles that dorsiflex the ankle and extend the toes originate on the lower leg.

Tibialis anterior arises from the lateral tibial condyle, shaft, and interosseus membrane. Fibularis (aka peroneus) longus, brevis, and tertius arise from the fibula (fibularis longus sometimes attaches to the lateral condyle of the tibia, as well). These muscles are "lateral compartment" muscles because they arise most laterally on the lower leg. Extensor digitorum longus arises from the lateral condyle of the tibia, the upper two-thirds of the medial fibula, and a small portion of the interosseous membrane. Extensor hallucis longus attaches along the medial fibula and interosseous membrane.

• Insertions of muscles that act on the ankle and foot:

Fibularis brevis and fibularis tertius insert on the proximal portion of metatarsal V. Extensor digitorum longus inserts on the bases of the middle and distal phalanges of toes 2-5. Extensor hallucis longus inserts at the base of the distal phalanx of digit 1, aka the big toe.