TABLE 13.1 Intrinsic Muscles on the Plantar Aspect of the Foot Muscle
Function Superficial Layer Flexor digitorum brevis Abductor hallucis Abductor digit minimi Second Layer Quadratus plantae Lumbricales Third Layer Adductor hallucis Flexor hallucis brevis Flexor digiti minimi Deepest Layer Plantar interossei (3) Dorsal interossei (4) MTP, metatarsophalangeal. Adduct and fl ex 3 lateral phalanges; support lateral longitudinal arch
Extend and abduct toes 2–4; help maintain parallel alignment of metatarsals during stance phase; stabilize forefoot during push-off phase of gait
Adducts great toe toward second toe Flexes great toe Flexes MTP of fi fth toe; contributes to lateral longitudinal arch stability Assists with stabilizing fl exor digitorum longus tendons Flex MTP joints and extend interphalangeal joints; maintain integrity of transverse arch during toe extension Assists fl exor digitorum longus with fl exing toes Abducts great toe; assists with fl exion of great toe Abducts fi fth toe; assists with fl exion of fi fth toe
Lumbricales Lumbricales Abductor hallucis
Abductor digiti minimi
Flexor digitorum brevis
Plantar fascia (cut) A B Second layer Figure 13.27 Layers of the intrinsic muscles of the foot. (A) Superficial layer. (B) Second layer. Continued
