Muscle & Actions
Name the three superficial posterior-compartment muscles
Gastrocnemius, soleus, and plantaris
Name the three lateral ankle collateral ligament bands
Anterior talofibular (ATFL), calcaneofibular (CFL), and posterior talofibular (PTFL)
What are the three components of non-weight-bearing pronation?
Dorsiflexion, eversion, and abduction.
Compare open-chain and closed-chain talocrural dorsiflexion arthrokinematics.
Open chain: convex talus rolls anteriorly and glides posteriorly in mortise (opposite). Closed chain: concave tibial mortise rolls and glides anteriorly on talus (same direction).
How does rearfoot varus in NWB commonly compensate during WB, and why does it matter for orthotic assessment?
Compensatory subtalar pronation may bring the medial forefoot toward the ground. Assess whether the deformity is flexible or rigid before selecting posting/support.
Name all three muscles of the deep posterior compartment
Tibialis posterior, flexor digitorum longus, and flexor hallucis longus
Which ligament primarily resists inversion with the ankle plantarflexed? Which is stressed by inversion near neutral/dorsiflexion?
ATFL resists plantar and inversion; CFL is stressed with inversion in neutral/dorsiflexion
Which malleolus is more distal and posterior, and how does this influence the talocrural axis?
The lateral malleolus lies more distal and posterior than the medial malleolus, producing an oblique talocrural axis.
Compare the posterior versus anterior/middle subtalar articular surface shapes and roll/glide rules.
Posterior: concave talus on convex calcaneus, so talar roll/glide same direction. Anterior/middle: convex talus on concave calcaneus, so talar roll/glide opposite directions.
Describe a pronation twist: what initiates it and which rays move?
With rearfoot/STJ supination and limited midtarsal adaptation, the forefoot compensates: 1st/2nd rays plantarflex and 4th/5th rays dorsiflex.
Which muscle provides the strongest dynamic support to the medial longitudinal arch and has a major pronation-control moment arm
Tibialis posterior
What do the extensor and fibular (peroneal) retinacula do?
Hold the tendons close to the ankle/foot and prevent bowstringing during movement
During ankle dorsiflexion, what motion occurs at the proximal tibiofibular joint?
The proximal fibula glides superiorly and posteriorly (with associated rotation).
Define the sinus tarsi and tarsal canal and identify their relationship to subtalar facets.
An oblique tunnel between the groove of the talus and calcaneus; lateral/anterior opening is sinus tarsi, medial continuation is tarsal canal. They separate posterior from anterior/middle facets.
Describe a supination twist: what initiates it and which rays move?
With rearfoot/STJ pronation and inadequate midtarsal accommodation: 1st/2nd rays dorsiflex and 4th/5th rays plantarflex.
List the intrinsic plantar muscles in layers 1 and 2
Layer 1: abductor hallucis, flexor digitorum brevis, abductor digiti minimi. Layer 2: quadratus plantae and lumbricals
Where are the cervical and interosseous talocalcaneal ligaments located?
Cervical ligament: more anterior in the sinus tarsi, between the talar and calcaneal necks. Interosseous talocalcaneal ligament: more medial in the tarsal canal, connecting talus and calcaneus.
An axis is 35° superior to the A-P axis. Which motion is dominant and what secondary motion is possible?
Frontal-plane inversion/eversion dominates around an axis closer to A-P; sagittal-plane dorsiflexion/plantarflexion contributes secondarily.
In WB pronation, describe calcaneal, talar, and tibial motions; contrast with WB supination.
WB pronation: calcaneal eversion, talar adduction and plantarflexion, tibial internal rotation. WB supination: calcaneal inversion, talar abduction and dorsiflexion, tibial external rotation.
What is the windlass mechanism during terminal stance?
Great-toe/MTP extension tensions plantar fascia, approximates calcaneus and metatarsal heads, raises arch, and helps form a rigid lever for propulsion.
List the intrinsic plantar muscles in layers 3 and 4, and identify the medial plantar nerve intrinsic targets.
Layer 3: flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis. Layer 4: plantar and dorsal interossei. Medial pantar nerve: abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, first lumbrical
Name talonavicular and calcaneocuboid ligament supports; what makes the spring ligament important?
Talonavicular: spring, deltoid, bifurcate, dorsal talonavicular. Calcaneocuboid: bifurcate, dorsal calcaneocuboid, short plantar, long plantar. Spring ligament supports the talar head and medial arch.
Describe the subtalar axis and explain why motion is triplanar.
The oblique subtalar axis is approximately 42° superior and 16° medial relative to A-P; inversion/eversion couples with abduction/adduction and small DF/PF to produce screw-like pronation/supination.
Explain the subtalar/transverse-tarsal locking relationship and how it changes terrain adaptability.
Subtalar supination promotes transverse-tarsal locking and a rigid lever; pronation unlocks the transverse-tarsal joint and increases adaptability. End-range supination is least adaptable.
Give two kinetic-chain contributors that may increase plantar fascia loading.
Examples: limited ankle dorsiflexion, excessive/prolonged pronation, impaired calf capacity, or altered first-MTP extension. These are clinical contributors, not sole causes.