Lower Extremity Muscles: Psoas, Iliacus & more

Lower Extremity Muscles

Psoas Major

• Hip flexion is its function.
• It connects the lumbar vertebrae to the lesser trochanter.
• Innervation is from the lumbar spinal nerves.

Iliacus

• Hip flexion primary function.
• Originates from the iliac fossa and attaches to the femur.
• Innervated by the femoral nerve.

Rectus Femoris

• Actions include knee extension and hip flexion.
• Originates at the anterior inferior iliac spine (AIIS).
• Inserts via the quadriceps tendon, patellar tendon, and tibial tuberosity.
• It is innervated by the femoral nerve.

Vastus Medialis

• Responsible for knee extension.
• Originates from the greater trochanter, intertrochanteric line, and linea aspera.
• Inserts via the quadriceps tendon, patellar tendon, and tibial tuberosity.
• Innervated by the femoral nerve.

Vastus Lateralis

• Knee extension is main function
• Originates from the greater trochanter, intertrochanteric line, and linea aspera.
• Insertion point through the quadriceps tendon, patellar tendon, and tibial tuberosity.
• It is innervated by the femoral nerve.

Vastus Intermedius

• Responsible for knee extension.
• Originates from the greater trochanter, intertrochanteric line, and linea aspera.
• Inserts via the quadriceps tendon, patellar tendon, and tibial tuberosity.
• Innervated by the femoral nerve.

Sartorius

• Hip flexion, knee flexion, abduction, and external rotation are its functions
• Originates at the anterior superior iliac spine (ASIS).
• Inserts on the medial surface of the tibia via the pes anserinus.
• Receives innervation from the femoral nerve.

Pectineus

• Hip adduction is its function.
• Originates from the pubic bone.
• Attaches to the Linea Aspera.
• Innervated by the obturator nerve.

Adductor Longus

• Hip adduction is main function.
• Originates from the pubic bone.
• Inserts on the Linea Aspera.
• Receives innervation from the obturator nerve

Adductor Brevis

• Its primary function is hip adduction.
• Originates from the pubic bone.
• Connects to the Linea Aspera.
• Innervated by the obturator nerve.

Gracilis

• Hip adduction is the primary function.
• Originates from the pubic bone.
• Inserts on the medial surface of the tibia through the pes anserinus.
• It is ennervated by the obturator nerve.

Adductor Magnus (Adductor Part)

• The adductor part functions in thigh adduction.
• Originates from the pubic bone.
• Inserts on the linea aspera.
• Supplied by the obturator nerve.

Adductor Magnus (Hamstring Part)

• Hip extension is the function of the hamstring part
• Originates from the pubic bone.
• Connects to the adductor tubercle.
• Innervated by the tibial division of the sciatic nerve.

Semimembranosus

• Hip extension and knee flexion are its identified functions.
• Originates from the ischial tuberosity.
• Inserts on the medial surface of the proximal tibia through the pes anserinus.
• Tibial division of the sciatic nerve provides innervation.

Semitendinosus

• Functions include hip extension and knee flexion.
• Originates from the ischial tuberosity.
• Connects to the fibular head.
• Innervated by the tibial division of the sciatic nerve.

Biceps Femoris (Long Head)

• Hip extension and knee flexion are its functions.
• Originates from the ischial tuberosity.
• Inserts on the fibular head.
• Tibial division of the sciatic nerve provides innervation

Biceps Femoris (Short Head)

• Knee flexion function.
• Originates from the linea aspera.
• Inserts on the fibular head.
• Innervated by the common fibular (peroneal) nerve.

Gluteus Maximus

• Hip extension from a flexed or relaxed position and external rotation.
• Originates from the posterior ilium and sacrum.
• Insertion on the gluteal tuberosity (femur) and IT band
• Innervated by the inferior gluteal nerve.

Gluteus Medius

• Functions include hip abduction and medial rotation.
• Originates from the posterior ilium.
• Connects to the greater trochanter.
• Innervated by the superior gluteal nerve.

Gluteus Minimus

• Hip abduction and medial rotation.
• Originates from the posterior ilium.
• Attaches to the greater trochanter.
• Supplied by the superior gluteal nerve.

Tensor Fascia Latae

• Hip abduction is its function.
• Connects from the ASIS and iliac crest to the IT band.
• Gets its nerve supply from the superior gluteal nerve.

Piriformis

• External rotation of the hip.
• Starts at the sacrum.
• Connects to the greater trochanter.

Gastrocnemius

• Plantarflexion and knee flexion are its functions..
• Originates from the medial and lateral femoral condyles.
• Inserts on the calcaneus via the calcaneal tendon.
• Innervated by the tibial nerve.

Soleus

• Plantarflexion is its function.
• Originates from the anterior fibula and tibia.
• Inserts onto the calcaneus via the calcaneal tendon.
• Supplied by the tibial nerve.

Flexor Hallucis Longus

• Plantarflexion and flexion of the big toe.
• Comes from the posterior fibula.
• Connects to the distal phalanx of the big toe.
• Innervated by the tibial nerve.

Tibialis Posterior

• Inversion and plantarflexion
• Arises from the posterior fibula.
• Attaches to the tarsal and metatarsal bones.
• Gets its nerve supply from the tibial nerve.

Flexor Digitorum Longus

• Plantarflexion and flexion of toes 2-5
• Originates from the posterior fibula.
• Inserts to the distal phalanges of toes 2-5.
• Innervated by the tibial nerve.

Fibularis (Peroneus) Longus

• Eversion and plantarflexion
• Originates from the proximal fibula.
• Inserts on the medial surface of the tarsal and metatarsal bones.
• Supplied by the superficial fibular (peroneal) nerve.

Fibularis (Peroneus) Brevis

• Eversion and plantarflexion
• Arises from the distal fibula.
• Inserts on the 5th metatarsal.
• Innervated by the superficial fibular nerve.

Tibialis Anterior

• Dorsiflexion and inversion
• Arises from the anterior tibia.
• It inserts on the plantar surface of the medial tarsal and metatarsal bones.
• Supplied by the deep fibular nerve.

Extensor Hallucis Longus

• Dorsiflexion and extension of the big toe.
• Originates from the anterior fibula.
• Connects to the distal phalanx of the big toe.
• It is innervated by the deep fibular nerve

Extensor Digitorum Longus

• Dorsiflexion and extension of toes 2-5 are the functions.
• Originates from the lateral tibial condyle and fibula.
• Inserts on the distal phalanges of toes 2-5.
• It is ennervated by the deep fibular nerve.

Fibularis (Peroneus) Tertius

• Dorsiflexion and eversion.
• Medial surface of the fibula
• Connects to the dorsal surface of digit 5.
• Innervated by the deep fibular nerve.

Obturator Externus

• Hip adduction is the identified fucntion.
• Originates from the pubic bone.
• Connects to the linea aspera.
• Innervated by the obturator nerve.

Superior Gemellus

• External rotation of the hip.
• Arises from the ischium.
• Connects to the greater trochanter.

Obturator Internus

• External rotation of the hip
• Originates from the ischium.
• Inserts on the greater trochanter.

Inferior Gemellus

• External rotation of the hip
• Originates from the ischium.
• Insertion point on the greater trochanter.

Quadriceps Femoris

• External rotation of the hip.
• Originates from the ischium.
• Connects to the greater trochanter.

Plantaris

• A function of this muscle is to flex the knee
• Originates from the lateral femoral condyle.
• Connects to the calcaneal tendon.
• Gets its nerve supply from the tibial nerve.

Popliteus

• Knee flexion (unlocks knee).
• Originates from the femoral epicondyle.
• Connects to the posterior tibia.
• Innervated by the tibial nerve.

Anterior Thigh Muscles

• Psoas major, iliacus, vastus medialis/intermedius/lateralis, sartorius and rectus femoris.

Medial Thigh Muscles

• Pectineus, adductor longus/brevis/magnus, obturator externus and gracilis

Posterior Thigh Muscles

• Semimembranosus, semitendinosus and biceps femoris (long and short head).

Gluteal Region Muscles

• Gluteus maximus/medius/minimus, superior/inferior gemellus, obturator internus, quadratus femoris, piriformis and tensor fascia latae.

Superficial Posterior Leg Muscles

• Gastrocnemius, plantaris and soleus muscles.

Deep Posterior Leg Muscles

• Flexor hallucis longus, tibialis posterior, flexor digitorum longus and popliteus.

Lateral Leg Muscles

• Fibularis (Peroneus) longus and brevis.

Anterior Leg Muscles

• Tibialis anterior, extensor hallucis longus, extensor digitorum longus and fibularis (peroneus) tertius.

Blood Supply to the Lower Extremity

Anterior Thigh

• Supplied by the femoral artery.

Posterior Thigh

• Deep artery of the thigh provides the blood.

Medial Thigh

• Obturator artery provides blood.

Anterior Leg

• Anterior tibial artery supplies blood.

Posterior Leg

• Blood provided by posterior tibial artery.

Lateral Leg

• Fibular artery supplies the blood.

Innervation Recap

Lumbar Spinal Nerve

• Psoas major is innervated by the lumbar spinal nerve.

Femoral Nerve

• Iliacus, rectus femoris, vastus medialis/intermedius/lateralis and sartorius are supplied by this nerve.

Obturator Nerve

• Pectineus, adductor longus/brevis/magnus, obturator externus and gracilis musclesare supplied by this nerve.

Tibial Division of Sciatic Nerve

• This nerve innervates the adductor magnus (hamstring), semimembranosus, semitendinosus and biceps femoris (long head).

Common Fibular (Peroneal) Nerve

• Biceps femoris (short head).

Inferior Gluteal Nerve

• Innervates the gluteus maximus.

Superior Gluteal Nerve

• Gluteus medius/minimus and tensor fascia latae.

Tibial Nerve

• Gastrocnemius, soleus, plantaris, flexor hallucis longus/digitorum longus, tibialis posterior and popliteus.

Superficial Fibular (Peroneal) Nerve

• Fibularis (peroneus) longus/brevis.

Deep Fibular Nerve

• Tibialis anterior, extensor hallucis longus/digitorum longus and fibularis (peroneus) tertius.

Overview of lower extremity muscles including the Psoas Major, Iliacus, Rectus Femoris, and Vastus Medialis. Details origin, insertion, innervation and function of each muscle. Focus on hip flexion and knee extension.