Anatomy Lower extremety

• O: Anterior Superior iliac spine
• I: Upper medial shaft of tibia
• A: Assists in; flexion of femur
•                     abduction of femur
•                     lateral rotation of femur
•                     flexion of knee
•                     medial rotation of tibia when knee is flexed and foot is unweighted
• N: Femoral

Longest muscle in the body, it is the most superficial thigh muscle and forms the lateral border of the femoral triangle.  Its name is derived from the Latin word for tailor, sartor, to indicate its action of bringing the leg into a cross-legged sitting position.  Not a powerful muscle, it only assists in these actions.

• O: Pelvic surface of sacrum
• I: Greater trochanter of femur
• A: Lateral rotation of hip. Assist in abduction when the hip is flexed.
• N: Sacral plexus

• O: Tuberosity of ischium
• I: Quadrate line
• A: Lateral rotation of hip. Assist in adduction of hip joint.
• N: Sacral plexus

• O: Spine of ischium
• I: Greater trochanter of femur
• A: Lateral rotation of hip. Assist in abduction when the hip is flexed.
• N: Sacral plexus

• O: Internal or pelvic surface of obturator membrane and margin of obturator foramen
• I: Greater trochanter of femur
• A: Lateral rotation of hip. Assist in abduction when the hip is flexed.
• N: Sacral plexus

• O: Tuberosity of ischium
• I: Greater trochanter of femur
• A: Lateral rotation of hip. Assist in abduction when the hip is flexed.
• N: Sacral plexus

• O: Rami of pubis and ischium and external surface of obturator membrane
• I: Greater trochanter of femur
• A: Lateral rotation of hip. Assist in adduction of hip joint.
• N: Obturator

Lie deep to gluteus maximus and inferior to gluteus medius. The sciatic nerve lies between the rotators and piriformis and may be entrapped or compressed by piriformis.  The first letter in the words of the phrase "Piece Goods Often Go On Quilts" denotes the anatomical order of these muscles from superior to inferior (piece goods = fabric sold by the yard)

• O: Lumbar vertebrae L1-5, transverse processes T12-L5 vertebrae - bodies and intervertebral discs
• I: Lesser trochanter of femur
• A: Flexion of femur, Flexion of trunk - lumbar spine, Assists lateral flexion of trunk - lumbar spine
• N: L2-3 spinal ns

Not present in most people.  When present, it is a small muscle with a long tendon lying in front of psoas major, originating on the 12th thoracic vertebra, inserting on the pelvic rim, and innervated by L1

• O:Iliac fossa of ilium
• I: Lesser trochanter of femur
• A: Flexion of femur
• N: Femoral

Psoas Major and Iliacus are referred to as the iliopsoas because of their common insertion an action.  Iliopsoas is the strongest hip flexor.  If the femrs are fixed, these muscles flex the lumbar spine such as when doing a sit-up.

Comprised of 4 large, anterior thigh muscles that insert below the knee and act to extend the knee.  The 3 vasti lie deep to rectus femoris and 2 (lateralis and medialis) have their origins on the posterior femur.

• O: Anterior inferior iliac spine & ilium at upper rim of acetabulum
• I: Patella & tibial tuberosity via patellar ligament
• A: Extension of knee and assists flexion of femur
• N: Femoral

Only muscle in the quads that originates on the pelvis and crosses both the hip and knee joints.  Its combined actions bring the leg forward in walking.  When the insertion is fixed, rectus femoris extends the knee as seen in jumping.  The term rectus, is derived from Latin word for straight, depicting this muscle that runs straight down the femur

• O: Linea aspera of femur & Intertrocanteric line of femur
• I: Patella & Tibial tuberosity via patellar ligament
• A: Extension of knee
• N: Femoral

Latin term for immense. These 3 muscles of the quads derive their name from their size and position.  Vastus lateralis is the largest of the group.

• O: Linea aspera of femur & Greater trochanter of femur
• I: Patella & Tibial tuberosity via patellar ligament
• A: Extension of knee
• N: Femoral

• O: Anterior and lateral femoral shaft
• I: Patella & Tibial tuberosity via patellar ligament
• A: Extension of knee
• N: Femoral

• O: Superior ramus of anterior pubis
• I: Pectineal line of femur, inferiorto lesser trochanter
• A: Flexion of femur, Adduction of femur, Assists medial rotation of femur
• N: Femoral

Includes medial thigh muscles that adduct the femur.  Adductor magnus, brevis, and longus assist in medial or lateral rotation of the femur, depending upon the starting position of the femur in extension or flexion.  Pectineus is the upper most muscle of the group.  Adductor magnus is the largest and deepest and most powerful of the group. Adductor brevis is superficial to adductor magnus and deep to adductor longus and pectineus.  Adductor longus is the most anterior of the adductors and gracilis is the most medial and weakest of the group.

Only hip adductor supplied by the femoral nerve, a fact explained by it being considered an estension of the iliopsoas.  However, like other hip adductors, it is sometimes supplied by a branch of the obturator nerve.

• O: Anterior pubis - body, inferior to pubic crest
• I: Linea aspera of femur - middle one third
• A: Adduction of femur, assists flexion of femur
• N: Obuturator

• O: Anterior pubis - body and inferior ramus
• I: Linea aspera of femur - proximal part, Pectineal line of femur
• A: Adductor of femur, assists flexion of femur
• N: Obturator

Adductor longus forms the medial border of the femoral triangle that contains the femoral nerve, artery, and vein. Adductor longus is referred to as the "long adductor" and adductor brevis as the "short adductor"

• O: Anterior head - inferior ramus of pubis.
•     Posterior head - ischial  tuberosity & ramus of ischium
• I: Posterior head - Linea aspera of femur
•    Anterior head - Adductor tubercle of femur
• A: Addustion of femur
•     Anterior head - assists flexion of femur and medial rotation of femur
•     Posterior head - assists extension of femur and lateral rotation of femur
• N: Anterior head - Obturator
•     Posterior head - Sciatic

The motions of the adductor magnus with its massive size and extensive attachments can vary depending upon which portion of the muscle is active and the starting position and direction of the movement of the femur.  At most, adductor magnus is an assistant in rotation.

• O: Inferior ramus of anterior pubis
• I: Medial proximal tibia
• A: Adduction of femur, assists flexion of knee and medial rotation of tibia when knee is flexed
• N: Obturator

Only muscle in the adductor group to cross the hip and knee joints.  The femoral shaft and the gracilis form the shape of the letter "V"

• O: Posterior sacrum, Ilium (via sacrotuberous ligament) and Posterior (superior) gluteal line of ilium
• I: Gluteal tuberosity of femur and Iliotibial tract (attaching to lateral condyle of tibia)
• A: Extension of femur and Lateral rotation of extended hip
• N: Inferior Gluteal

Greek for rump. The 3 gluteal muscles lie superficial to deep: gluteus maximus; gluteus medius; and gluteus minimus. Gluteus maximus is used mostly for power, as in going upstairs, rising from a sitting position, climbing or running rather than walking.  Similar to other lower extremity muscles, the gluteus maximus can move the femur against the pelvis (hip extension) or move the pelvis against the femur  (posterior pelvic tilt)

• O: Ilias crest of ilium, Ilium - between posterior (superior) and anterior (middle) gluteal lines
• I: Greater trochanter of femur
• A: Abduction of femur
•     anterior fibers do medial rotation of femur
• N: Superior gluteal

When standing on one foot, gluteus medius contracts on that side to helf stabalize the pelvis and prevent it from tilting to the unsupported side. Paralysis of this muscle on one side results in the "gluteus medius limp" : the pelvis tilts towards the uninvolved side in walking.

• O: Posterior ilium - between anterior (middle) and inferior gluteal lines
• I: Anterior surface of greater trochanter of femur
• A: Abduction and Medial rotation of femur
• N: Superior gluteal

Works with anterior portion of gluteus medius to steady the pelvis during ipsilateral weight-bearing

• O: Iliac crest - posterior to anterior superior iliac spine
• I: Iliotibial tract (attaches to the lateral condyle of the tibia
• A: Assist in; flexion of femur, abduction of femur, medial rotation of femur, stability of extended knee in standing and ambulation & extension of knee
• N: Superior gluteal

enclosed in fascia of the lateral thigh that extends as the iliotibial band to attach to the tibia.  When TFL conctracts, this tightens the fascia and helps stabilize the hip and knee joints.

• O: Ischial tuberosity
• I: Head of fibula - lateral aspect & Lateral condyle of tibia
• A: Extension & Flexion of knee, Lateral rotation of tibia when knee is flexed
• N: Sciatic - Tibial division

• O: Linea aspera
• I: Head of fibula - lateral aspect & lateral condyle of tibia
• A: Flexion of knee & Lateral rotation of tibia when knee is flexed
• N: Sciactic - Fibular division

• O: Ischial tuberosity
• I: Anterior proximal tibial shaft
• A: Extension of femur, Flexion of knee and Medial rotation of tibia when knee is flexed
• N: Sciatic - Tibial division

• O: Ischial tuberosity
• I: Posterior medial tibial condyle
• A: Extension of femur, Flexion of knee and Medial rotation of tibia when knee is flexed
• N: Sciatic - tibial division

Insert medially at the knee while the biceps femoris inserts laterally.  These insertions account for the medial rotation of the tibia by the semitendinosus and lateral rotation of the tibia by the biceps femoris.

• O: Lateral condyle of femur
• I: Posterior proximal tibial shaft
• A: Lateral rotation of the femur to "unlock" the extended knee to initiate knee flexion.  Assists medial rotation of tibia when knee is flexed
• N: Tibial

Lateral rotation of the femur to "Unlock" the extended knee to initiate knee flexion

Deepest muscle on the posterior of the knee joint.  Because of its action in lateral rotation of the femur, popliteus is remembered as "the key that unlocks the knee". It is said to "reverse its origin and insertion", laterally rotating the femur on the tibia or medially rotating the tibia on the femur, depending upon which is fixed.

• O: Lateral epicondyle of femur
• I: Calcaneus via calcaneal tendon
• A: Assists plantarflexion of ankle and flexion of knee
• N: Tibial

Superficial on the posterior of the knee joint, lying between the soleus and gastrocnemius muscles.  It is the lower extremity counterpart of the palmaris longus of the hand and is absent in some persons.  Gastrocnemius, soleus and plantaris share a common insertion, the calcaneal tendon.

• O: Posterior fibula
• I: Distal phalanx of great toe - plantar surface
• A: Flexion of great toe at MP joint and IP joint. Assists plantarflexion of ankle
• N: Tibial

"Harry" of Tom, Dick and Harry calf muscles.  Flexor hallucis longus plays an important role in forward propulsion by flexing the big toe to push off the ground when walking and running.

• O: Posterior tibia
• I: Distal phalanges of 4 lateral toes - plantar surface
• A: Flexion of 4 lateral toes at IP joints. 
•     Assists flexion of 4 lateral toes at MP joints
•     Assists plantarflexion of ankle
• N: Tibial

"Dick" of Tom, Dick and Harry calf muscles. Comparable to the flexor digitorum profundus in the hand.

• O: Posterior tibia, Posterior fibula, Interosseous membrane
• I: Navicular tarsal bone, Adjacent tarsals and metatarsals on plantar surface
• A: Inversion of foot & Assists plantarflexion
• N: Tibial

"Tom" of Tom, Dick and Harry calf muscles.  Deepest of the three muscles.

• O: Soleal line of tibia, Posterior head of fibula, Upper shaft of fibula
• I: Calcaneus via calcaneal tendon
• A: Plantarflexion of ankle
• N: Tibial

Resembles the sole, a flat fish.  Deep to gastrocnemius, soleus is the stronger plantarflexor and is fatigue-resistant.  Together, the gastrocnemius and soleus are referred to as the triceps surae and are powerful plantarflexors of the ankle for raising the heel in running and jumping.

Thick tendon of insertion of the triceps surae into the calcaneus, connecting the calf (soleus and gastrocnemius) muscles to the heel.  Strongest tendon in the body.

• O: Medial head - Medial epicondyle of femur
•     Lateral head - Lateral epicondyle of femur
• I: Calcaneal tendon
• A: Plantarflexion of ankle & Assists flexion of knee
• N: Tibial

Gastro is Greek for belly.  Can act on the knee or the ankle seperately, but not simultaneously.  The "gastroc" raises the heel during running and jumping.

• O: Lateral condyle of tibia, Lateral shaft of tibia & Interosseous membrane
• I: Base of 1st metatarsal - plantar surface, Medial cuneiform tarsal bone - plantar surface
• A: Dorsiflexion of ankle & Inversion of foot
• N: Deep fibular

Strongest dorsiflexor of the ankle and enables the toes to clear the ground in ambulation.  Paralysis of the muscle causes foor drop. "Shin splints" result from overuse of this muscle.

• O: Lateral condyle of tibia, Proximal 2/3 of anterior shaft of fibula
• I: Middle and distal phalanges of 4 lateral toes
• A: Extension of 4 lateral toes at MP joints & Assists dosiflexion of ankle
• N: Deep fibular

Comparable to the extensor digitorum in the hand and its tendons comprise the extensor expansion of the foot.

• O: Anterior shaft of fibula, Interosseous membrane
• I: Base of distal phalanx of the great toe
• A: Extension of great toe at IP joint and MP joint & Assists dorsiflexion of ankle
• N: Deep fibular

Comparable to the extensor pollicis longus in the hand

• O: Anterior distal fibula (with extensor digitorum longus)
• I: Base of 5th metatarsal
• A: Eversion of foot & Assists dorsiflexion of foot
• N: Deep fibular

Considered to be a part of extensor digitorum longus.  Places the foot flat on the ground by raising the lateral border.  It contracts reflexively when the foot is over-inverted thus preventing ankle injury

• O: Head and lateral shaft of fibula - upper 2/3
• I: Base of first metatarsal - plantar surface, Medial cuneiform tarsal bone - plantar surface
• A: Eversion of foot & Assists plantarflexion of ankle
• N: Superficial fibular

• O: Lateral shaft of fibula - lower 2/3
• I: Base of 5th metatarsal - lateral surface
• A: Eversion of foot & Assists plantarflexion of ankle
• N: Superficial fibular

The action of the foot evertors (as well as invertors) is especially helpful when walking or running on uneven surfaces.  Sometimes the muscles "give out", and a sprained ligament can result.