Muscles of the Plantar Foot Flashcards
Layer 1 (3)
- Abductor hallucis
- Abductor digiti minimi
- Flexor digitorum brevis
“ABs Flex”
Layer 2 (4)
- Flexor digitorum longus
- Flexor hallucis longus
- Quadratus plantae
- Lumbricals
“Flex Flex QP L”
Remember that it is longus and not brevis because the lumbricals are found in the longus tendons
Layer 3 (3)
- Adductor hallucis
- Flexor digiti minimi brevis
- Flexor hallucis brevis
“AD Flexes”
Layer 4 (2)
- Dorsal interosseous
- Plantar interosseous
Abductor hallucis
1st layer
- Large muscle which has an expanded portion wich forms a HOOD over the porta pedis (tom, dick, very nervous harry)
- This makes sense because the flexor retinacula creates the porta pedis on the medial side of the foot where the abductor hallucis would run to go to the hallux
Origin of abductor hallucis
- Medial process of calcaneal tuberosity (FFA)
- Flexor retinaculum
- Plantar aponeurosis
- Intermuscular septum between itself and flexor digitorum brevis (1st layer)
Insertion of abductor hallucis
- Medial side, plantar surface of the base of the proximal phalanx
- Medial sesamoid of the 1st MPJ (possibly)
Innervation of abductor hallucis
- Medial plantar nerve
Action of abductor hallucis
- Abducts the first digit
Flexor digitorum brevis
1st layer
o Lies deep to central part of plantar aponeurosis
o Lateral plantar nerves and vessels are found deep to it
Origin of flexor digitorum brevis
o Plantar aponeurosis
o Medial and lateral intermuscular septa
o Medial process of calcaneal tuberosity (FFA)
Insertion of flexor digitorum brevis
One tendon attaches to each of the 4 lateral digits:
- Each runs in the tendon sheath of flexor digitorum longus until it reaches the base of the proximal phalanx
- At this point, it divides into two slips
- Slips diverge from each other to surround the tendon of the flexor digitorum longus
- Reunite to lie deep to flexor digitorum longus
- Slips divide again to insert into the middle phalanges of the lateral 4 digits
Innervation of flexor digitorum brevis
Medial plantar nerve
Function of flexor digitorum brevis
o Flex the proximal interphalangeal joints of lateral 4 digits
o Flex the metatarsophalangeal joints
Variation of flexor digitorum brevis
o The tendon to the 5th digit may be absent
Abductor digiti minimi
1st layer
o Lies superficial along the lateral margin of the foot
Origin of abductor digiti minimi
o Lateral processes of calcanea tuberosity
o Medial processes of calcanea tuberosity
o Depression between these two processes
o Note: this is the A in MLAP, LLAP and LA
Insertion of abductor digiti minimi
o Runs through a groove on plantar surface of the 5th met
o Inserts into lateral side of the plantar surface of the
base of the proximal phalanx of the 5th digit (same as flexor digiti minimi brevis)
Function of abductor digiti minimi
- Abduct 5th digit
- Flex 5th digit
Variation in abductor digiti minimi
- May be an accessory insertion into base of 5th metatarsal
- If present, forms a separate muscle: abductor os metatarsal digiti minimi
Second layer
NOTE
- The lateral plantar aponeurosis lies between the 1st and 2nd layers of muscle
Muscles of the 2nd layer
- Flexor digitorum longus
- Flexor hallucis longus
- Quadratus plantae
- Lumbricals
Quadratus plantae
2nd layer
- AKA flexor accessorius
- Two heads of origin, which are separated by the long plantar ligament
- Medial head is larger
Origin of quadratus plantae
- Medial head: medial process of calcaneal tuberosity
- Lateral head: lateral process of calcaneal tuberosity
Insertion of quadratus plantae
- Tendon of flexor digitorum longus
- Note that fivers from both heads unite together to insert
Innervation of quadratus plantae
Trunk of lateral plantar nerve
Function of quadratus plantae
- Accesory flexor of lateral 4 digits
- Helps flexor digitorum longus by putting tension on its tendon and straightening the line of pull of the long flexor
Variation of quadratus plantae
- The entire muscle, or just the lateral head may be absent