Overview
This lecture covers tips and mnemonics for memorizing the skeletal muscles of the lower limb, including origins, insertions, actions, and groupings.
Major Hip Muscles
- Iliopsoas is composed of the iliacus and psoas major, serving as the primary hip flexors.
- Iliacus originates from the ilium; psoas major from vertebral bodies; both insert on the femur.
- Psoas minor is a weak, variable muscle that may flex the spine but not the hip.
- Gluteal muscles: maximus (largest), medius, and minimus—all originate on the ilium and insert on the femur.
- Gluteus maximus inserts via the iliotibial band (IT band), which it shares with the tensor fasciae latae (TFL).
- TFL helps tense fascia laterally and assists with hip movement.
Deep Hip Rotators
- Piriformis is located inferior to gluteus minimus and is stretched in pigeon pose.
- Gemellus superior and inferior are twin muscles, with obturator internus between them.
- Obturator internus originates from obturator foramen; obturator externus is outside the hip.
- Quadratus femoris is a square-shaped muscle attaching to the femur and is most inferior.
Thigh Muscles
- Sartorius is the longest muscle, running from pelvis to tibia, and enables hip and knee movements.
- Quadriceps group (rectus femoris, vastus lateralis/intermedius/medialis) extend the knee; rectus femoris also flexes the hip.
- Hamstrings: biceps femoris (lateral), semitendinosus (medial, tendinous), semimembranosus (medial, membranous); extend hip, flex knee.
- Adductor group (magnus, longus, brevis, gracilis, pectineus) adduct thigh; gracilis is long and thin, pectineus is most superior.
Lower Leg Muscles
- Anterior: tibialis anterior (dorsiflexes foot), extensor digitorum longus (extends toes), extensor hallucis longus (extends big toe), fibularis tertius (dorsiflexes and everts foot).
- Lateral: fibularis longus, brevis, tertius; all evert the foot and originate from the fibula.
- Posterior: gastrocnemius and soleus plantarflex the foot and share the Achilles tendon; plantaris is a small plantar flexor.
- Popliteus unlocks the knee for flexion.
Deep Posterior Leg & Foot Muscles
- Tom, Dick, and Harry: tibialis posterior (arch support), flexor digitorum longus (toe flexion), flexor hallucis longus (big toe flexion).
- Plantar foot: flexor digitorum brevis (flexes toes), abductor hallucis (abducts big toe), abductor digiti minimi (abducts pinky toe), quadratus plantae (assists toe flexion).
- Dorsal foot: extensor digitorum brevis, extensor hallucis brevis (extend toes), dorsal interossei (abduct toes).
- Plantar interossei adduct toes; lumbricals flex and adduct toes.
Key Terms & Definitions
- Iliopsoas — primary hip flexor muscle composed of iliacus and psoas major.
- Gluteus maximus — largest gluteal muscle; main hip extensor.
- Tensor fasciae latae (TFL) — lateral hip muscle that tenses fascia.
- Quadriceps — group of four muscles extending the knee.
- Hamstrings — group of three muscles extending hip and flexing knee.
- Adductors — medial thigh muscles bringing legs together.
- Tibialis anterior — dorsiflexes the ankle.
- Fibularis group — muscles that evert the foot.
- Gastrocnemius/Soleus — main calf muscles for plantar flexion.
- Tom, Dick, and Harry — mnemonic for tibialis posterior, flexor digitorum longus, flexor hallucis longus.
Action Items / Next Steps
- Review and memorize muscle groupings and their main functions.
- Practice identifying muscle origins, insertions, and actions.
- Use mnemonics provided to reinforce memory of muscle order/relationships.