Thigh muscles anatomy with diagram

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Thigh Muscles Anatomy

The thigh is divided into three compartments by fascial septa, each containing a distinct muscle group with its own nerve supply and function.

Diagrams

Anterior & Medial View - All Thigh Muscle Groups

Anterior and medial view of thigh muscles including quadriceps, adductors, and sartorius

Lateral View - Superficial Thigh Muscles

Lateral view showing sartorius, rectus femoris, vastus lateralis, biceps femoris, iliotibial tract

Quadriceps Femoris Schematic (Anterior Compartment)

Schematic showing all four heads of quadriceps femoris with origins and insertions

Posterior Thigh (Hamstrings) Schematic

Schematic of hamstrings showing biceps femoris, semimembranosus, semitendinosus origins and insertions

1. Anterior Compartment (Extensors)

Innervated by the femoral nerve (L2-L4).

Sartorius


Origin	Anterior superior iliac spine (ASIS)
Insertion	Medial tibial tuberosity (pes anserinus, with gracilis + semitendinosus)
Action	Hip: flexion, abduction, external rotation; Knee: flexion + internal rotation
Nerve	Femoral nerve (L1-L4)

The sartorius is the longest muscle in the body. It crosses both the hip and knee, acting as a biarticular muscle. At the knee level, it migrates posteriorly to contribute to the pes anserinus ("goose foot").

Quadriceps Femoris (4 heads + articularis genus)

All four heads converge onto the tibial tuberosity via the patellar ligament. The patella is a sesamoid bone embedded in the quadriceps tendon.

Head	Origin
Rectus femoris	Anterior inferior iliac spine (straight head); acetabular roof (reflected head)
Vastus medialis	Medial lip of linea aspera; distal intertrochanteric line
Vastus lateralis	Lateral lip of linea aspera; lateral surface of greater trochanter
Vastus intermedius	Anterior femoral shaft
Articularis genus	Distal femoral shaft (tightens suprapatellar recess during extension)

Insertion (all): Tibial tuberosity via patellar ligament; medial/lateral patellar retinacula
Action: Knee extension (all 4); hip flexion (rectus femoris only)
Nerve: Femoral nerve (L2-L4)

Clinical note: Quadriceps weakness or paralysis prevents active knee extension. The patient compensates by hyperextending the knee so the line of gravity shifts anterior to the joint axis, allowing passive stability through posterior capsule and ligaments.

2. Medial Compartment (Adductors)

Innervated primarily by the obturator nerve (L2-L4). The adductor magnus has dual supply (obturator + tibial nerve).

Muscle	Origin	Insertion	Action
Adductor longus	Anterior pubis	Middle third of linea aspera	Adduction, flexion
Adductor brevis	Body/inferior ramus of pubis	Upper linea aspera	Adduction
Adductor magnus	Inferior pubic ramus to ischial tuberosity	Linea aspera (adductor part) + adductor tubercle (hamstring part)	Adduction; hamstring part = hip extension
Adductor minimus	Inferior pubic ramus	Linea aspera (proximal)	Adduction
Pectineus	Pectineal line of pubis	Pectineal line of femur	Adduction, flexion
Gracilis	Body/inferior ramus of pubis	Medial tibial tuberosity (pes anserinus)	Adduction; knee flexion + internal rotation

Key facts:

The adductor magnus is the largest adductor - it makes up ~27% of total thigh muscle mass and ~60% of adductor mass.
The adductor hiatus is a gap in the adductor magnus where the femoral artery and vein pass from the anterior thigh into the popliteal fossa.
The adductors' primary functions are adduction, some extension, and medial rotation; together with lower abdominal muscles they stabilize the pelvis during activity.
Among athletes, adductor longus is the most commonly injured adductor muscle.

3. Posterior Compartment (Hamstrings / Flexors)

Innervated by the tibial nerve (L5-S2), except the short head of biceps femoris (common fibular nerve, L5-S2). All originate from the ischial tuberosity (except the short head of biceps).

Muscle	Origin	Insertion	Action
Biceps femoris (long head)	Ischial tuberosity + sacrotuberous ligament	Head of fibula	Hip extension/adduction; knee flexion + external rotation
Biceps femoris (short head)	Lateral lip of linea aspera (middle third)	Head of fibula	Knee flexion + external rotation
Semimembranosus	Ischial tuberosity	Medial tibial condyle; oblique popliteal ligament	Hip extension/adduction; knee flexion + internal rotation
Semitendinosus	Ischial tuberosity + sacrotuberous ligament	Medial tibial tuberosity (pes anserinus)	Hip extension/adduction; knee flexion + internal rotation

Key facts:

The hamstrings are biarticular - they cross both the hip and knee. This creates two types of muscle insufficiency:
- Passive insufficiency: with knee extended, hamstrings are too short to allow full hip flexion (tight hamstrings in straight leg raise)
- Active insufficiency: with hip extended, hamstrings cannot shorten enough for maximal knee flexion
Semitendinosus and semimembranosus produce internal rotation at the knee; biceps femoris produces external rotation.
Among professional soccer players, the hamstrings are the second most commonly injured muscle group (28%), after quadriceps (32%).

Compartment Summary

Compartment	Muscles	Nerve	Primary Action
Anterior	Sartorius, Quadriceps femoris (x4 + articularis genus)	Femoral nerve	Knee extension; hip flexion
Medial	Adductor longus/brevis/magnus, Pectineus, Gracilis, Adductor minimus	Obturator nerve (+ tibial for adductor magnus)	Hip adduction
Posterior	Biceps femoris, Semimembranosus, Semitendinosus	Tibial nerve (sciatic)	Knee flexion; hip extension

Sources: General Anatomy and Musculoskeletal System, THIEME Atlas of Anatomy; Imaging Anatomy Text and Atlas Vol. 3, Bones, Joints, Vessels and Nerves

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