Anatomy of the Ankle and Foot

Introduction to Biomechanics of the Ankle and Foot

• The ankle and foot provide a stable base while conforming to uneven surfaces
• They provide balance and stability, and are flexible to absorb stress and adapt to the ground
• They are also rigid to withstand propulsive forces and push off

Functions of the Ankle and Foot

• They provide important protective and feedback measures to the muscles of the lower extremity
• They enable weight bearing during walking, running, and standing
• They facilitate propulsion and power generation
• They allow positioning of the foot

Tibiofibular Joints

• The proximal tibiofibular joint (PTFJ) is a plane joint between the head of the fibula and the posterolateral aspect of the tibia
• The distal tibiofibular joint (DTFJ) is a syndesmosis between the concave face of the tibia and the convex face of the fibula
• The PTFJ has anterior and posterior proximal tibiofibular ligaments, and an interosseous membrane
• The DTFJ has anterior and posterior distal tibiofibular ligaments, and fibrous fat tissue connecting the tibia and fibula

Arthrokinematics of the Tibiofibular Joints

• The PTFJ has a slight gliding motion during osteokinematics of the ankle and knee
• Dorsiflexion and plantar flexion of the ankle cause a cranial and caudal glide, respectively
• Knee flexion and extension cause a forward and posterior glide, respectively
• The DTFJ has a separation and approximation during dorsiflexion and plantar flexion, respectively

Anatomy of the Ankle and Foot

• The ankle is a talocrural joint composed of the tibia, fibula, and talus
• The foot is composed of all tarsal bones and joints distal to the ankle
• The rearfoot includes the talus, calcaneus, and subtalar joint
• The midfoot includes the navicular, cuboid, and three cuneiforms
• The forefoot includes the metatarsals and phalanges, including all distal joints and the tarsometatarsal joints

Talocrural Joint

• The talocrural joint is a hinge joint with one degree of freedom
• The rest position is 10° of plantar flexion
• The compact position is achieved through maximal dorsiflexion
• The concave/convex rule applies to the joint: open kinetic chain (OKC) follows the convex rule, and closed kinetic chain (CKC) follows the concave rule

Osteokinematics of the Talocrural Joint

• The range of motion is 0-20/30° of dorsiflexion and 0-50° of plantar flexion

Arthrokinematics of the Talocrural Joint

• Dorsiflexion and plantar flexion have different arthrokinematic patterns in OKC and CKC
• In OKC, dorsiflexion involves a posterior slide and anterior roll of the talus, and plantar flexion involves an anterior slide and posterior roll
• In CKC, dorsiflexion involves an anterior slide and anterior roll of the mortise, and plantar flexion involves a posterior slide and posterior roll

Talocrural Joint Stability

• Static stabilizers include the mortise and talar shape, gravity, capsule, and ligaments
• Dynamic stabilizers include the musculature
• Medial stability is provided by the deltoid ligament, which includes the tibionavicular, tibiotalar, and tibiocalcaneus ligaments
• Lateral stability is provided by the anterior talofibular ligament, posterior talofibular ligament, and calcaneofibular ligament

Kinetics of Dorsiflexion and Plantarflexion

• Dorsiflexion is primarily achieved by the tibialis anterior muscle
• Plantar flexion is primarily achieved by the gastrocnemius muscle
• The ankle is less stable in plantar flexion