Anatomy of the Ankle and Foot Joints

Foot and Ankle Joints

• The foot and ankle have multiple joints, including major and minor ones.
• The joints work together as a complex system.

Outline

• Aims: Identifying major joints and cavities, motions, muscular control, and neurovascular structures supplying the joints.

• Main Joints, Joint Cavities, and Motions: Subtalar, anterior talocalcaneal, talonavicular, calcaneocuboid, cuneonavicular, intercuneiforms, medial cuneometatarsal, cuboidometatarsal, talocrural.

• Muscular control of the joints: Dorsiflexors (tibialis anterior, extensor digitorum longus, extensor hallucis longus), plantarflexors (gastrocnemius, soleus, plantaris, tibialis posterior, flexor hallucis longus, flexor digitorum longus, peroneus longus, peroneus brevis).

• Neurovascular structures supplying the joints: Blood supply to malleoli, talus (branches of dorsalis pedis) and anastomosis around the complex. Nerve supply from branches of deep peroneal and tibial nerves.

Major Joints/Cavities - Foot 1

• Subtalar (posterior talocalcaneal) joint: Talus, calcaneus articulations
• Anterior talocalcaneal joint: Talus, calcaneus
• Talonavicular joint: Talus and navicular
• Calcaneocuboid joint: Calcaneus and cuboid
• Talocalcaneonavicular joint: Talus, calcaneus, navicular; collectively known as the midtarsal joint.

Major Joints/Cavities - Foot 2

• Cuneonavicular joint: Navicular, medial cuneiform
• Intercuneiform joints: Cuneiform bones
• Cuneocuboid joint: Lateral cuneiform, cuboid
• Medial cuneometatarsal joint: 1st cuneiform & metatarsal
• Cuboidometatarsal joint: 4th & 5th metatarsals and cuboid
• These joints are part of one continuous cavity.

Major Joints/Cavities - Foot 3

• Ankle (talocrural) joint: Tibia, fibula, talus
• Metatarsophalangeal joints: Metatarsals & toes
• Interphalangeal joints: Phalanges (toes)

The Ankle Joint

• Articulation of the tibia and fibula with the talus, forming a mortise into which the talus fits
• Synovial hinge joint, with capsule and synovial membrane
• The true ankle joint (talocrural) works as part of a complex system of joints.

Ankle Cross-Section

• Includes blood vessels and nerves (e.g., dorsalis pedis artery, deep peroneal nerve, superficial peroneal nerve, tibial nerve, posterior tibial artery, etc.).
• Shows the location and arrangement of major structures.

Bones

• Shows the distal tibiofibular joint, lateral malleolus, medial malleolus, tibia, fibula, tibial plafond, trochlear surface of talus, and sustentaculum tali (of calcaneus).

Bones (Anterior-posterior X-Ray)

• Different bones are labeled with numbers.

Lateral Ligaments

• Anterior talofibular ligament
• Posterior talofibular ligament
• Calcaneofibular ligament
• Injuries to these ligaments are common.

Medial Ligaments

• Stronger than lateral ligaments.
• Posterior tibiotalar ligament, tibiocalcaneal ligament.
• Anterior tibiotalar ligament & tibionavicular ligament.
• Includes the word 'deltoid'.

Posterior View

• Posterior tibiotalar
• Posterior tibiofibular
• Transverse tibiofibular
• Calcaneofibular
• Tibiocalcaneal

Anterior(ish) View

• Interosseous membrane
• Anterior tibiotalar ligaments
• Calcaneofibular ligaments

Ankle Joint Motion

• Primarily plantarflexion and dorsiflexion
• More plantarflexion than dorsiflexion
• Stable in dorsiflexion
• Some inversion, eversion, minimal abduction, adduction

Muscles & Ankle Motion

• Dorsiflexors: Tibialis anterior, extensor digitorum longus, extensor hallucis longus
• Plantarflexors: Gastrocnemius, soleus, plantaris, tibialis posterior, flexor hallucis longus, flexor digitorum longus, peroneus longus, peroneus brevis

Neurovascular Supply of the Ankle

• Blood vessel branches supplying the malleoli.
• Talus's blood supply (head and neck)
• Talus vulnerability to blood supply interruption if fractured.
• Nerve branches of the deep peroneal and tibial nerves.

Subtalar Joint

• Articulation between the posterior, inferior talus and the superior calcaneus
• Synovial, plane joint with capsule attached to margins of articular surfaces.
• Gliding and rotary motion.
• Sinus tarsi and canal penetrate the joint.

Subtalar Articulation

• Shows the talus sitting on the 'shelf' of the calcaneus.
• Parts of the joint are labeled (e.g., anterior talocalcaneal articulation).

Anatomical Variations

• The number of facets varies.

STJ Ligaments (Subtalar Joint Ligaments)

• Interosseous talocalcaneal ligament; limits inversion and eversion.
• Lateral talocalcaneal ligament, limits inversion.
• Posterior talocalcaneal ligament, relatively insignificant.

STJ Motions

• Pronation and supination
• Movement depends on whether the foot is on or off the ground.
• In OKC, talus part of foot; In CKC, talus part of leg.
• Tri-planar simultaneous movement.

Broadly Speaking: Pronation and Supination

• Pronation: Shock absorbency, mobile adapter for terrain.
• Supination: Aids propulsion, helps turn foot to rigid lever.

OKC Motion

• The talus is free to move.
• Pronation: Abduction, eversion, dorsiflexion
• Supination: Adduction, inversion, plantarflexion

CKC Motion

• The talus is locked between the malleoli; part of the leg.
• Pronation: Adduction, inversion, plantarflexion.
• Supination: Abduction, eversion, dorsiflexion.

CKC Motion 2

• Provides a table of movements for both Pronation and Supination with respect to the Talus and Tibia.

Muscles & STJ Motion

• Pronators: Peroneus brevis, longus, EDL.
• Supinators: Tibialis posterior, anterior, FHL, gastrocnemius, soleus, plantaris.

Neurovascular Supply to STJ

• Blood supply via branches of the posterior tibial and peroneal arteries and sinus tarsi
• Anastomosis around the complex.
• Nerve supply from deep peroneal and maybe some tibial nerves.

Talocalcaneonavicular Joint

• Anterior talocalcaneal+talonavicular joint.
• Talus, sitting on 'shelf' of calcaneus, articulates with navicular.
• Spring ligament integral to joint

The Midtarsal Joint Complex

• Not one anatomical joint but a pair (talonavicular and calcaneocuboid) acting as a functional unit.

TCN Joint Ligaments (Talocalcaneonavicular)

• Dorsal talonavicular ligament
• Plantar calcaneonavicular (spring) ligament; integral part of TCN joint; elastic.

Calcaneocuboid Joint

• Articulation between the distal calcaneus and proximal cuboid.
• Synovial, encloses capsule, plane joint.

CC Joint Ligaments (Calcaneocuboid)

• Bifurcated ligament (Y-shaped): Calcaneonavicular, calcaneocuboid portions.
• Dorsal calcaneocuboid
• Long plantar ligament: Calc to cuboid & base of metatarsals
• Short plantar ligament: Calc to cuboid

Midtarsal Joint Motions

• MTJ motion closely related to ankle and STJ.
• Talus is common to all 3 joints.
• As STJ pronates, MTJ becomes more mobile for uneven terrain; locks for rigid lever when STJ supinates.

MTJ Joint Motions 2

• Traditional theories suggest two independent MTJ axes (longitudinal and oblique).
• Motions combine to produce pronation/supination.
• Theories on MTJ mechanisms and associated motions have changed with time.

Muscles & MTJ Motion

• Pronators: Peroneus longus, brevis, tertius, EDL.
• Supinators: Tibialis anterior, extensor hallucis longus, tibialis posterior, FHL &FDL (medial fibres may supinate).

Neurovascular Supply to MTJ

• Anastomosis from dorsalis pedis, medial & lateral plantar arteries provides blood.
• Nerves from deep peroneal, medial & lateral plantar nerves.

Other Inter-tarsal Joints

• Cuneonavicular (3 joints, smooth gliding synovial joints strengthens by ligaments
• Intercuneiforms
• Cuneocuboid
• Cuboideonavicular joints: fibrous joints, strong dorsal, plantar & interosseous ligaments.
• Cuboidometatarsal and intercuneiform joints
• Also tarsometatarsal joints

Intermetatarsal Joints

• Articulations between metatarsal bases; synovial, plane joints; supported by dorsal, plantar and interosseous ligaments.

Tarsometatarsal Joints

• Articulations between tarsal and metatarsal bones; 1st jt cavity, 2nd recessed, and stable; connected by dorsal, plantar and interosseous ligaments.

Rays of the Forefoot

• 1st ray: Medial cuneiform & 1st metatarsal
• 2nd ray: Intermediate cuneiform & 2nd metatarsal
• 3rd ray: Lateral cuneiform & 3rd metatarsal
• 4th ray: 4th metatarsal
• 5th ray: 5th metatarsal

What are Rays?

• One or more bones acting as a unit (e.g. 1st ray plantarflexes into lever for propulsion; 1st & 5th usually independent).

Effects of Pronation

• STJ pronation unlocks MTJ for uneven terrain accommodation; dorsiflexes 1st ray and internally rotates tibia.

Effects of Supination

• STJ supination unlocks MTJ for propulsion; plantarflexes 1st ray; facilitates normal gait

Metatarsophalangeal (MTP) Joints

• All MTP joints are similar; exception: 1st (often different)
• Large, convex metatarsal head; smaller, concave proximal phalanx.
• 1st MTP articulates with sesamoids; synovial, condyloid joints.

Muscles That Cross the MTPJ

• Hallux: EHL, EHB, EDB, FHL, FHB, ADH, ABH
• Lesser toes: EDL, EDB, FDL, FDB, PADs, DABs, lumbricals, ABDM, FDMB.

Motions at MTPJs

• Primarily extension/flexion; some abduction/adduction; negligible frontal plane rotation.

Ligaments of the MTPJs

• Tough fibrous capsule surrounds joints
• Thickened at sides (collateral ligaments)
• Thickened on plantar surface (plantar plate)
• Hallux has intersesamoidal ligament & plantar sesamoidal ligament; deep transverse metatarsal ligaments
• Lesser toes (plantar plates)

Plantar Plates

• Lesser toes (fibrocartilaginous thickening of the joint capsule) provide attachment points for plantar aponeurosis, flexor sheaths, DTML and collateral ligaments and extensor expansion. 1st toe has sesamoid apparatus.

Plantar MTPJs

• Shows fibrous capsule, plantar plate, 1st plantar ligament, FHL and FHB/OADH.

Neurovascular Supply to MTPJs

• Blood from dorsal digital arteries & plantar metatarsal/digital arteries (IPJs)
• Nerve supply: dorsal digital, common & proper plantar digital nerves for IPJs; nail mainly supplied by plantar nerves.

Interphalangeal (IP) Joints

• 1 in big toe, 2 in other toes, synovial, hinge joints.
• Primarily flexion more than extension
• PIPJ moves more than DIPJ

Muscles/Tendons Crossing the IPJs

• Muscles crossing PIPJ: FDL, EDL, FDB, EDB, lumbricals.
• Muscles crossing DIPJ: FDL, EDL, lumbricals.
• Muscles crossing IPJ of hallux: EHL & FDL

Extensor Expansion

• Extensor tendons widen and flatten and blend with fascia surrounding toes.
• Splits into 3 parts; central part inserts into intermediate phalanx and others to distal phalanx base.

Flexor Sheaths

• Synovial sheaths cover flexor tendons; thicker at the phalanges; thinner and more lax over IPJs.
• Proximal end blends with plantar aponeurosis.

Flexor Tendons

• Flexor digitorum brevis splits to allow FDL access to the distal phalanx.

Neurovascular Supply to IPJs

• Blood supply from plantar and dorsal digital arteries.
• Nerve supply from proper plantar and dorsal digital nerves.