Lower Limb

Gluteus Maximus

Origin:

• Ilium behind the posterior gluteal line

• Dorsal surface of sacrum and coccyx

• Sacrotuberous ligament

Insertion:

• Superficial ¾ → iliotibial tract

• Deep ¼ → gluteal tuberosity of femur

Nerve: Inferior gluteal nerve (L5, S1, S2)

Action:

• Main and strongest extensor of the hip joint

• Essential in:

• Rising from sitting position

• Climbing stairs

• Running

• Lateral rotation of the hip joint

Clinical:

• Inferior gluteal nerve injury causes:

• Weak hip extension

• Weak lateral rotation

• Difficulty rising from sitting

• Difficulty climbing stairs

Gluteus Medius

Origin: Gluteal surface of ilium between anterior and posterior gluteal lines

Insertion: Lateral surface of greater trochanter

Nerve: Superior gluteal nerve

Action:

• Main abductor of the thigh

• Anterior fibers medially rotate the thigh

• Prevents pelvic tilt during walking and running

• Stabilizes pelvis when opposite limb is raised

Clinical:

• Superior gluteal nerve injury →

• Loss of abduction

• Positive Trendelenburg sign

• Lurching gait (unilateral lesion)

• Waddling gait (bilateral lesion)

Gluteus Minimus

Origin: Gluteal surface of ilium between anterior and inferior gluteal lines

Insertion: Front (anterior surface) of greater trochanter

Nerve: Superior gluteal nerve

Action:

• Abducts thigh

• Anterior fibers medially rotate thigh

• Stabilizes pelvis during walking

• Prevents pelvic drop on unsupported side

Clinical:

• Same as gluteus medius:

• Positive Trendelenburg sign

• Lurching gait

• Waddling gait

Tensor Fasciae Latae (TFL)

Origin:

• ASIS

• Adjacent anterior part of iliac crest

Insertion: Iliotibial tract

Nerve: Superior gluteal nerve

Action:

• Flexes hip

• Abducts thigh

• Medially rotates thigh

• Tightens fascia lata

• Helps stabilize knee through iliotibial tract

Piriformis

Origin: Pelvic surface of sacrum

Insertion: Upper border of greater trochanter

Nerve: Nerve to piriformis (S1, S2)

Action:

• Lateral rotation of extended thigh

• Abduction of flexed thigh

• Stabilizes hip joint

Obturator Internus

Origin: Internal surface of obturator membrane and surrounding bone

Insertion: Medial surface of greater trochanter

Nerve: Nerve to obturator internus (L5, S1)

Action:

• Lateral rotation of thigh

• Abduction of flexed thigh

• Stabilizes femoral head

Superior Gemellus

Origin: Ischial spine

Insertion: Tendon of obturator internus

Nerve: Nerve to obturator internus (L5, S1)

Action:

• Lateral rotation of thigh

• Stabilizes hip joint

Inferior Gemellus

Origin: Ischial tuberosity

Insertion: Tendon of obturator internus

Nerve: Nerve to quadratus femoris (L4, L5, S1)

Action:

• Lateral rotation of thigh

• Stabilizes hip joint

Quadratus Femoris

Origin: Lateral border of ischial tuberosity

Insertion: Quadrate tubercle on intertrochanteric crest

Nerve: Nerve to quadratus femoris (L4, L5, S1)

Action:

• Powerful lateral rotation of thigh

• Assists adduction

• Stabilizes hip joint

Obturator Externus

Origin: External surface of obturator membrane and surrounding bone

Insertion: Trochanteric fossa

Nerve: Obturator nerve (L3, L4)

Action:

• Lateral rotation of thigh

• Stabilizes head of femur in acetabulum

ILIOPSOAS (= Psoas Major + Iliacus)

Origin:

Psoas Major → Bodies and transverse processes of T12–L5 vertebrae

Iliacus → Iliac fossa

Insertion: Lesser trochanter of femur

Nerve:

Psoas Major → Lumbar plexus (L1–L3)

Iliacus → Femoral nerve

Action:

• Strongest flexor of hip

• Flexes trunk on thigh

• Flexes thigh on trunk

• Assists lateral rotation of hip

Clinical:

• Weakness → difficulty climbing stairs

• Psoas abscess may produce flexed hip posture

SARTORIUS (Longest muscle in the body)

Origin: ASIS

Insertion: Upper medial surface of tibia (Pes anserinus)

Nerve: Femoral nerve

Action:

• Flexes hip

• Abducts hip

• Laterally rotates hip

• Flexes knee

• Medially rotates leg when knee is flexed

Cross-legged sitting position

(Flexion + Abduction + Lateral rotation)

Clinical:

• Forms lateral boundary of femoral triangle

RECTUS FEMORIS

Origin:

Straight head → AIIS

Reflected head → Superior rim of acetabulum

Insertion:

Quadriceps tendon → Patella

Patellar ligament → Tibial tuberosity

Nerve: Femoral nerve

Action:

• Extends knee

• Flexes hip

Only quadriceps muscle crossing both:

• Hip joint

• Knee joint

VASTUS LATERALIS

Origin:

• Greater trochanter

• Lateral lip of linea aspera

Insertion:

• Quadriceps tendon

• Patella

• Tibial tuberosity

Nerve: Femoral nerve

Action:

• Extends knee

VASTUS MEDIALIS

Origin:

• Intertrochanteric line

• Medial lip of linea aspera

Insertion:

• Quadriceps tendon

• Patella

• Tibial tuberosity

Nerve: Femoral nerve

Action:

• Extends knee

• Stabilizes patella

Clinical:

• Weakness → lateral patellar displacement

VASTUS INTERMEDIUS

Origin: Anterior and lateral surfaces of femoral shaft

Insertion:

• Quadriceps tendon

• Patella

• Tibial tuberosity

Nerve: Femoral nerve

Action

• Extends knee

TENSOR FASCIAE LATAE

Origin:

• ASIS

• Adjacent iliac crest

Insertion: Iliotibial tract

Nerve: Superior gluteal nerve

Action:

• Flexes hip

• Abducts hip

• Medially rotates hip

• Tightens fascia latae

• Stabilizes knee

PECTINEUS

Origin: Pectineal line of superior pubic ramus

Insertion: Pectineal line of femur (below lesser trochanter)

Nerve: Femoral nerve (occasionally obturator contribution)

Action:

• Adducts hip

• Flexes hip

ADDUCTOR LONGUS

Origin: Body of pubis

Insertion: Middle third of linea aspera

Nerve: Obturator nerve

Action:

• Adducts thigh

• Assists hip flexion

Clinical:

• Forms medial boundary of femoral triangle

ADDUCTOR BREVIS

Origin: Body and inferior ramus of pubis

Insertion: Upper linea aspera

Nerve: Obturator nerve

Action:

• Adducts thigh

• Assists flexion