Talocrural. Synovial / hyaline between upper facet of talus and inferior facet of tibia.
- modified hinge; axis of rotation changes b/n extremes of plantarflexion and dorsiflexion
- stabilised by medial and lateral malleoli (grip talar sides)
Attached: articular margins all three bones except talus where fixed in front of articular margin on neck.
- posteriorly on tibia is attached also to posterior tibiofibular ligament.
Attached to articular margin of talus, clothes intracapsular neck, elsewhere ¨ articular margins
Capsule is lined with it.
Deltoid: medially in deep part (narrow band tibial malleolus ¨ side of talus);
- and superficial part: triangular, from borders of med malleolus ¨ medial tubercle of talus, along sustentaculum tali and spring ligament to navicular tuberosity
Lateral: arises from lateral malleolus as bands
- i) anterior talofibular ligament = anterior band ¨ talus
- ii) calcaneofibular ligament = intermediate band ¨ lateral calcaneus
- iii) posterior talofibular = posterior band ¨ lateral tubercle of talus
- iv) posterior tibiofibular = posterior band, covered with hyaline ¨ articulates with talus
- In plantarflexion the posterior ligaments lie edge-to-edge; in dorsiflexion they separate like the edges of scissors.
Anterior and posterior tibial arteries and peroneal
Deep peroneal and tibial nerves
Upper facet of talus is concave side-side and convex AP; broad in front, narrow behind.
Dorsiflexion: broad anterior area grasped by mortice of malleoli and inferior tibial surface
- to allow this the fibular must rotate slightly, stretching at the inferior syndesmosis and gliding at the superior tibiofibular joint.
- 10o, by tibialis anterior, long toe extensors, peroneus tertius
Plantarflexion: although smallest width articulating, eversion / inversion still impossible.
- 20o by gastroc & soleus assisted by long and short peronei and long flexors
Axis of rotation: slopes down and laterally (as though inversion in plantarflexion and eversion in dorsiflexion)
Anterior: b/n tendons of extensor hallucis and digitorum longus avoiding damage to deep peroneal nerve and anterior tibial vessels.
Behind medial malleolus: displace tendons of tibialis posterior and FDL forwards
Lateral displace peroneus longus and brevis forwards
Aspiration: in front of lateral malleolus lateral to tendon of peroneus tertius
- or in front of medial malleolus medial to tibialis anterior
- define jt line by moving foot.
Important joints: talus-navicular-calcaneus and calcaneus-cuboid
There are two separate joints under the talus: talocalcanean jt and talocalcaneonavicular jt
Ball (head of talus) and socket (concave navicular surface, and concave upper calcaneus facet)
- between these articulates with fibrocartilaginous upper spring ligament.
- enclosed in a single synovial capsule
Behind above jt. Synovial b/n concave facet under talus and convex facet on upper calcaneus
3) Calcaneocuboid jt
Separate synovial jt; front of calcaneus ¨ back of cuboid; capsule around it
- forms mid-tarsal jt with talonavicular part of talocalcaneonavicular jt
- short and long plantar ligaments are accessory ligaments on its plantar surface
- simple gliding movement during inversion / eversion
Thick bundle in hollows between anterior calcaneus ¨ cuboid
Covers the above ligament. From tuberosity of calcaneus ¨ posterior cuboid and superficial fibres, which bridge grove of cuboid ¨ fibrous ridge over peroneus longus ¨ anterior cuboid ¨ bases of central three metatarsal bones.
- covered by flexor accessorius and posterior part is visible in gap between its heads
Very strong, from anterior sustentaculum tali ¨ plantar surface of navicular
- upper surface articulates with talar head via a fibrocartilaginous facet
- is not elastic
From upper calcaneus (under extensor digitorum brevis) ¨ two heads
- medial limb ¨ navicular; lateral limb ¨ cuboid
Obliquely b/n talocalcaneonavicular jt and talocalcaneal jt
- open at lateral end like a funnel
- occupied by interosseous talocalcaneal ligament, vascular channels and cervical ligament between neck of talus and upper calcaneus
Inversion: accompanied by adduction and supination
- range of inversion is increased in plantarflexion; fully inverted foot is also plantarflexed
- tibialis anterior, tibialis posterior, assisted by extensor and flexor hallucis longus
Eversion: accompanied by abduction and pronation
- peroneus longus, brevis and tertius
- all inverting/everting muscles are attached anterior to the midtarsal joint.
Limitation to midtarsal mobility is provided by plantar ligaments and spring ligament
- they then transmit rotatory force to calcaneus (inverting or everting)
- axis is along a line from lateral tubercle of calcaneus through neck of talus medial tarsal sinus
- muscles thus pull at right angle to this axis.
Metatarsus is more rigid that metacarpus
1st Tarsometatarsal Jt
Own capsule, synovial membrane. Can move in a vertical plane.
- hyperextended in Ôflat footÕ(normally conforms to arch movements.
- There is no opposition like the thumb jt.
2nd tarsometatarsal
Immobile; base of metatarsal ¨ anterior medial and lateral cuneiform.
- fixed because axis of foot shifted through here; also slender, \ ¨ march #
1st metatarsophalangeal jt
site of hallux valgus; big toe has no dorsal extensor expansion nor fibrous flexor sheath
- long tendons are held in position by strands of deep fascia.
- if phalanges displaced laterally, fibrous bands give way, pull of EHL ¨ oblique ¨ increases the deformity.
Similar to hand with capsules and collateral ligaments
Erect, heel, lateral margin of foot, and pads of distal phalanges touch the ground.
- medial margin arches up ¨ medial longitudinal arch
- lateral bones do not bear equal pressure: much flatter lateral longitudinal arch.
Transverse arch is really only 1/2 an arch.
Integrity of arches maintained by bony, ligamentous and muscular factors.
Calcaneus, talus, navicular and three cuneiforms & metatarsals.
- pillars = tuberosity of calcaneus posteriorly and heads of medial metatarsals anteriorly.
Bony factors: unimportant
Ligaments: important, most from plantar aponeurosis (like a bowstring between the supporting pillars)
- if shortened by extension (especially of hallux) ¨ heightens arch
- also spring ligament: supports talar head; if it stretches the head sinks between navicular and calcaneus whereas it is meant to be the highest part of the arch.
Muscles: indispensable. FHL tendon crucial assisted by FDL to 2nd & 3rd toes (slip from FHL)
- act as bowstrings along medial edge, drawing arch pillars together
- short muscles of first layer likewise assist.
- In standing weight is borne on heel and ligaments take strain; until they ÔtireÕ and relief is obtained by pressing pads of toes on ground ¨ muscles maintain arch.
In propulsion, inertia and momentum of body through vastly greater strain on arch.
- FHL takes most tension
Tibialis anterior and peroneus longus inserted into same two bones (medial cuneiform &
first metatarsal) but exert differing effects:
- peroneus tends to evert flattening arch
- tib ant and post tend to invert, accentuating the medial curve.
No bony factors
Ligaments: critical: plantar aponeurosis in lateral part and plantar ligaments = bowstrings
Tendon of peroneus longus pulls up on the arch = most important single factor
- FDL (4th and 5th) assist and muscles of first layer also help separate arch pillars
Bones: Intermediate and lateral cuneiforms are wedge shaped ¨ maintain transverse arch
- lateral cuneiform overhangs cuboid a little ¨ rests on it
- however medial cuneiform wedged other way ¨ unhelpful for arch \ mixed effect of bones.
Ligaments: bind together cuneiforms and metatarsal bases = more important
Tendon of peroneus longus = most important; approximates arch borders across sole
Contraction of soleus and gastroc plantarflexes \ chief factor for propulsion
- much enhanced by arching of foot and flexion of toes (flexes a mobile foot)
Sequence of events in walking:
Heel strike ¨ support (weight bearing) ¨ toe-off ¨ swing
- weight successively: heel ¨ lateral border ¨ ball ¨ ant pillar of med arch & medial 3 digits
- in running heel remains off ground, toes and forefoot taking thrust of weight instead.
At heel strike, extensors contract, then gradually relax (prevents toes from slapping down)
- while heel rising, medial toes gradually extended ¨ elongated FHL & FDL ¨ increases force of their next contractions
- contraction of toe flexors heights medial arch ¨ increases force of take-off
Meanwhile lumbricals ¨ prevents toes buckling under when FLD pulls