Muscles of the Hip Flexors

Study Notes

Iliacus & Psoas major are the strongest hip flexors
Iliacus originates from the iliac fossa in the pelvis, while Psoas major originates from the transverse processes of lumbar vertebrae
Both muscles insert at the lesser trochanter of the femur.
Both muscles are innervated by the femoral nerve (L1-L3)
Sartorius is a long strap muscle that flexes the hip, extends the knee and is crucial for external rotation and abduction of the knee.
It originates at the anterior superior iliac spine (ASIS) and inserts at the pes anserine.
It is innervated by the femoral nerve (L2-L3)
Tensor Fascia Latae originates at the anterior iliac crest & inserts on the Iliotibial band.
It is innervated by the superior gluteal nerve (L4, L5,S1) and functions as a hip abductor
Rectus Femoris is the only muscle of the quadriceps that crosses the hip joint.
It originates at the anterior inferior iliac spine (AIIS) and inserts on the tibial tuberosity
Rectus Femoris is innervated by the femoral nerve (L2-L4) and functions to flex the hip and extend the knee.

The Gluteus Maximus is the primary hip extensor.
Gluteus Maximus originates from the posterior ilium and inserts at the gluteal tuberosity.
It is innervated by the Inferior Gluteal Nerve (L5, S1, S2)

Gluteus Medius and Gluteus Minimus are the primary hip abductors
Gluteus Medius and Gluteus Minimus originate from the lateral ilium and insert at the greater trochanter.
They are innervated by the Superior Gluteal Nerve (L4, L5, S1) .

Adductor longus, brevis and magnus muscles make up the adductor group.
They originate from the pubis and insert onto the linea aspera of the femur
They are innervated by the Obturator nerve.
Pectineus originates from the superior pubic ramus and inserts into the femur
It is innervated by the Femoral Nerve (L2-L3)
Gracilis originates from the inferior pubic ramus and inserts on the medial tibial surface.
It is innervated by the Obturator nerve from the common fibular branch and functions to adduct the hip.

The Quadriceps muscles (rectus femoris, vastus lateralis, vastly medialis and vastus intermedius) extend the knee.
All Quadriceps muscles insert on the tibial tuberosity
They are innervated by the Femoral nerve (L2-L4)

Semitendinosus, semimembranosus and biceps femoris (long and short head) are the hamstring muscles.
They flex the knee and extend the hip.
Semimembranosus and semitendinosus originate from the ischial tuberosity and insert on the medial tibial surface.
Bicep Femoris (long head) originates at the ischial tuberosity and inserts on the head of the fibula
Bicep Femoris (short head) originates on the linea aspera and inserts on the head of the fibula.
All hamstring muscles are innervated by the sciatic nerve, with some being innervated by specific branches of the nerve.

Tibialis Anterior, Extensor Digitorum Longus, and Extensor Hallucis Longus are the ankle dorsiflexors.
Tibialis Anterior originates from the lateral tibial condyle and inserts on the medial cuneiform and the base of the 1st metatarsal.
Extensor Digitorum Longus originates from the lateral tibial condyle and inserts on the distal phalanges of the toes.
Extensor Hallucis Longus originates from the medial surface of the fibular shaft and inserts on the base of the distal phalanx of the hallux.
All three ankle dorsiflexors are innervated by the deep fibular nerve (L4, L5).

Soleus, Gastrocnemius and Plantaris are all ankle Plantarflexors and are part of the triceps surae muscle group.
Soleus originates from the posterior fibers of the fibula and the medial fibers of the tibia.
Gastrocnemius originates from the medial and lateral condyles of the femur.
Plantaris originates from the lateral supracondylar line of the femur.
They all insert onto the Achilles tendon.
All of these muscles are innervated by the Tibial nerve (S1-S2).

Tibialis anterior dorsiflexes and inverts the foot
Tibialis Posterior plantarflexes and inverts the foot
Tibialis Posterior originates from the interosseous membrane, the posterior surface of the tibia, and inserts on the navicular, cuneiforms and metatarsals 2-4.
It is innervated by the tibia nerve.

Fibularis Longus and Fibularis Brevis are responsible for everting the foot.
Fibularis longus originates from the fibula and inserts on the 1st metatarsal.
Fibularis Brevis originates from the inferior 2/3 of the fibula and inserts on the 5th metatarsal.
Both muscles are innervated by the superficial fibular nerve (L5, S1, S2)

Flexor Digitorum Longus and Flexor Hallucis Longus are the primary toe flexors.
Flexor Digitorum Longus originates from the posterior surface of the tibia and inserts onto the toes 2-4.
Flexor Hallucis Longus originates from the posterior surface of the tibia and inserts onto the big toe.
Both are innervated by the Tibial Nerve.

The muscles of the foot are divided into 4 layers:
First Layer: abductor hallucis, flexor digitorum brevis and abductor digiti minimi.
** Second Layer:** quadratus plantae and lumbricals.
Third Layer: flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis.
Fourth Layer: dorsal interossei and plantar interossei.
All Muscles of the foot are innervated by the Tibial Nerve.