Provides a strong but mobile base of support structured to meet its functions:
Stability - base of support and rigid lever for propulsion
Mobility - adaptor to terrain, shock absorption
The Ankle (Talocrural) Joint
Mortise and tenon arrangement between the tibia/fibula and talus - inherently stable
Classified as a synovial hinge joint - uniaxial / strong set of collateral ligaments
Articular Surfaces - 3 areas to describe - continuous with each other and all covered with hyaline cartilage
Lateral triangular facet on body of the talus articulates with corresponding facet on fibula (lateral malleolus)
Medial comma shaped facet on body of the talus articulates with corresponding facet on medial malleolus
Trochlea (pulley shaped) surface on body of talus articulates with inferior aspect of lower end of tibia
Articular surfaces provide ankle with inherent stability
Motion permitted into dorsiflexion / plantarflexion
Capsule :
attached to articular margins of tibia, fibula and talus except anteriorly
to neck of talus anteriorly (weakest part of capsule to allow plantarflexion)
Synovial membrane attached to all articular margins, lines capsule and covers neck of talus
The Ankle (Talocrural) Joint - Ligaments
2 sets of strong collateral ligaments
Medially (continuous and collectively known as the Deltoid ligament) arise from the medial malleolus
Anterior tibiotalar (green)
Tibionavicular (brown)
Tibiocalcaneal (blue)
Posterior tibiotalar (red) (Each named according to its attachments)
Lateral collateral ligaments - 3 distinct structures arising from the lateral malleolus – weaker than the medial collateral
Anterior talofibular (blue)
Calcaneofibular (green)
Posterior talofibular (red) Each named according to its attachments
In addition to the collateral ligaments there are thickenings in the anterior and posterior capsule - anterior and posterior ligaments
Role of the ligaments is to limit:
Plantarflexion - anterior ligaments
Calcaneal adduction/abduction (component of inversion/eversion) - calcaneal ligaments
Dorsiflexion - posterior and calcaneal ligaments
Close packed position of the ankle is dorsiflexion
Loose packed position is plantarflexion (least stable)
The Calcaneus
Lies immediately below talus
Largest bone in foot
Role is to provide attachments for calf muscle and act as a short lever for propulsion
Points to note:
Sustentaculum tali
Peroneal tubercle
Medial and lateral tubercles (plantar aspect)
Articular facets
Superior - for talus
Anterior - for midtarsal joint
Subtalar Joint
Synovial modified multiaxial joint
Between posterior facet on superior aspect of calcaneus (convex)
and concave facet on inferior aspect of body of talus
Has a loose capsule attaching to articular margins
Ligaments :
Interosseous ligament - Found in sinus tarsi (from sulcus tali above to sulcus calcanei below
Reinforced medially by:
Medial talocalcaneal ligament - medial talar tubercle to posterior border of sustentaculum tali
Limits abduction of the calcaneum
Reinforced laterally by:
Cervical ligament - from lateral aspect of neck of talus to anterior part of sinus tarsi
Lateral talocalcaneal ligament - from lateral talar tubercle to lateral aspect of posterior calcaneum
Both limit adduction of calcaneum
Midtarsal Joint
Complex joint made up of the calcaneum and talus posteriorly and cuboid and navicular anteriorly
Anatomically divided into
Talocalcaneonavicular joint (medially)
Calcaneocuboid joint (laterally)
Talocalcaneonavicular Joint
Synovial modified ball and socket joint
Head of talus (ball) articulates with
posterior facet on navicular, superior facets on calcaneum and superior surface on ‘Spring’(plantar calcaneo-navicular) ligament (socket)
All covered in hyaline cartilage except Spring ligament - simple capsule lined with synovial membrane
Calcaneocuboid Joint
Forms lateral part of midtarsal joint
Synovial saddle joint
Between posterior cuboid and anterior calcaneum
Both articular surfaces covered in hyaline cartilage
Capsule extends just beyond articular surfaces and lined with synovial membrane
Ligaments of the Midtarsal Joint
5 to consider
Dorsal:
Dorsal talonavicular ligament
Bifurcate ligament
Plantar:
Spring (plantar calcaneonavicular) ligament - from sust. Tali to navicular
Short plantar (Plantar calcaneocuboid) ligament - anterior tubercle to cuboid
Long plantar ligament – medial and lateral tubercles to bases of 4 lateral metatarsals
Inversion & Eversion
Complex movements made up of the combined accessory movements occurring at the subtalar and midtarsal joints
Inversion - adduction at the subtalar joint and supination at the midtarsal joint
Eversion - abduction at the subtalar joint and pronation at the midtarsal joint
Surface Anatomy
Surface markings of the ankle joint area line passing from a point 2cm above the tip of the medial malleolus to a point 3cm above the lateral malleolus
Surface markings of the ligaments are done by identifying the relevant bony points
Midtarsal joint - a line concave proximally passing from a point just proximal to the navicular tuberosity to a point 1cm proximal to the tip of the styloid process of the base of the 5th metatarsal
