hips and legs

semitendinosus

• Location: Posterior thigh → tibia

• Action: Flexes knee, extends hip

• Synergists (from list): Semimembranosus, biceps femoris, gluteus maximus

• Antagonists (from list): Quadriceps group (knee extension), iliacus/psoas (hip flexion)

semimembranosus

• Location: Posterior thigh → tibia

• Action: Flexes knee, extends hip

• Synergists (from list): Semitendinosus, biceps femoris, gluteus maximus

• Antagonists (from list): Quadriceps, iliacus/psoas

biceps femoris

• Location: Posterior thigh → fibula

• Action: Flexes knee, extends hip

• Synergists (from list): Semitendinosus, semimembranosus, gluteus maximus

• Antagonists (from list): Quadriceps, iliacus/psoas

illacus

• Location: Iliac fossa → femur

• Action: Flexes hip

• Synergists (from list): Psoas major/minor, rectus femoris, sartorius

• Antagonists (from list): Gluteus maximus, hamstrings

psoas major and minor

• Location: Lumbar vertebrae → femur

• Action: Flexes hip

• Synergists (from list): Iliacus, rectus femoris, sartorius

• Antagonists (from list): Gluteus maximus, hamstrings

[major is bigger and more significant]

gluteus maximus

• Location: Largest buttock muscle; ilium, sacrum, coccyx → femur (gluteal tuberosity) & iliotibial tract

• Action: Extends and laterally rotates hip; powerful in rising from sitting, climbing stairs

• Synergists (from list): Hamstrings (semitendinosus, semimembranosus, biceps femoris — hip extension), teres major/latissimus dorsi (extension/adduction assist at shoulder, but hip focus is hamstrings)

• Antagonists (from list): Iliacus, psoas major/minor, rectus femoris, sartorius (hip flexion)

Gluteus medius

• Location: Lateral buttock; ilium → greater trochanter of femur

• Action: Abducts and medially rotates thigh; stabilizes pelvis during walking

• Synergists (from list): Gluteus minimus, tensor fascia latae (abduction/medial rotation)

• Antagonists (from list): Adductors (magnus, longus, brevis), gracilis (hip adduction)

gluteus minimus

• Location: Deep to gluteus medius; ilium → greater trochanter of femur

• Action: Abducts and medially rotates thigh; stabilizes pelvis

• Synergists (from list): Gluteus medius, tensor fascia latae

• Antagonists (from list): Adductors (magnus, longus, brevis), gracilis

tensor fasciae latae (TFL)

• Location: Lateral hip → iliotibial tract

• Action: Abducts and medially rotates thigh; stabilizes knee via IT band

• Synergists (from list): Gluteus medius, gluteus minimus

• Antagonists (from list): Adductors (magnus, longus, brevis), gracilis, gluteus maximus (extension/adduction)

rectus femoris

• Location: Anterior thigh → patella/tibia

• Action: Extends knee, flexes hip

• Synergists (from list): Vastus group (knee extension), iliopsoas (hip flexion)

• Antagonists (from list): Hamstrings (knee flexion, hip extension)

vastus lateralis

• Location: Lateral anterior thigh → patella/tibia

• Action: Extends knee

• Synergists (from list): Vastus medialis, vastus intermedius, rectus femoris

• Antagonists (from list): Hamstrings

vastus medialis

• Location: Medial anterior thigh → patella/tibia

• Action: Extends knee

• Synergists (from list): Vastus lateralis, vastus intermedius, rectus femoris

• Antagonists (from list): Hamstrings

vastus intermedius

• Location: Deep anterior thigh → patella/tibia

• Action: Extends knee

• Synergists (from list): Vastus lateralis, vastus medialis, rectus femoris

• Antagonists (from list): Hamstrings

sartorius

• Location: Long strap muscle, anterior superior iliac spine → tibia

• Action: Flexes, abducts, laterally rotates hip; flexes knee

• Synergists (from list): Iliopsoas, rectus femoris (hip flexion)

• Antagonists (from list): Gluteus maximus (hip extension), adductors (hip adduction)

gracilis

• Location: Medial thigh → tibia

• Action: Adducts thigh, flexes knee

• Synergists (from list): Adductors (magnus, longus, brevis)

• Antagonists (from list): Gluteus medius/minimus, TFL (abduction)

adductors (Longus; superficial, brevis; beneath, Magnus; largest and deepest)

• Location: Medial thigh → femur

• Action: Adduct thigh

• Synergists (from list): Gracilis

• Antagonists (from list): Gluteus medius/minimus, TFL

tibialis anterior

• Location: Anterior shin → medial foot

• Action: Dorsiflexes and inverts foot

• Synergists (from list): None

• Antagonists (from list): Gastrocnemius, soleus (plantar flexion), fibularis group (eversion)

tibialis posterior

• Location: Deep posterior leg → foot

• Action: Plantar flexes and inverts foot

• Synergists (from list): Gastrocnemius, soleus (plantar flexion)

• Antagonists (from list): Tibialis anterior (dorsiflexion)

fibularis longus

• Location: Lateral leg → foot

• Action: Everts and plantar flexes foot

• Synergists (from list): Fibularis brevis

• Antagonists (from list): Tibialis anterior (inversion/dorsiflexion)

fibularis brevis

• Location: Lateral leg → foot

• Action: Everts and plantar flexes foot

• Synergists (from list): Fibularis longus

• Antagonists (from list): Tibialis anterior

gastrocnemius

• Location: Superficial calf → calcaneus via Achilles tendon

• Action: Plantar flexes foot, flexes knee

• Synergists (from list): Soleus, tibialis posterior

• Antagonists (from list): Tibialis anterior (dorsiflexion)

soleus

• Location: Deep calf → calcaneus via Achilles tendon

• Action: Plantar flexes foot

• Synergists (from list): Gastrocnemius, tibialis posterior

• Antagonists (from list): Tibialis anterior