Ankle and Foot Joint Biomechanics: Kinematics and Stability
Talocrural Joint (Tibiotalar) Kinematics
Osteokinematics (Movement Ranges)
- Dorsiflexion: 10º to 20º
- Plantar Flexion: 40º
Arthrokinematics (Joint Surface Movement)
- Dorsiflexion: The talus slips posteriorly and medially. The fibula moves upward. The axis of dorsiflexion is oblique, passing through the tips of the two malleoli.
- Plantar Flexion: The talus slips anteriorly and laterally. The fibula moves downward.
Joint Stability Mechanisms
The talus does not rotate within the tibiofibular mortise. It is more stable in dorsiflexion than in plantar flexion because its anterior leading edge is wider.
Injury to the interosseous membrane or the ligament connecting the tibia and distal fibula can change the distribution of pressure, potentially leading to an overload of the tibiotalar joint.
Lateral stability is achieved by the coupling between the two joint surfaces. As long as the two malleoli are intact, the tibiotalar joint remains stable laterally.
Anteroposterior stability is significantly influenced by the posterior border of the tibia (the posterior malleolus). Studies have shown that a loss due to fracture and subsequent rise of the middle posterior ridge causes a decrease of 35% in articular contact.
Subtalar Joint Kinematics
Osteokinematics
- Inversion: 40º
- Eversion: 20º
Arthrokinematics
- Inversion: The calcaneus slips toward the medial arch.
- Eversion: The calcaneus slips toward the lateral arch.
Midtarsal Joint Kinematics
Osteokinematics
Pronation and Supination.
Ankle Muscle Groups
- Anterior Compartment: Tibialis anterior, Extensor Digitorum Longus, Extensor Hallucis Longus, Peroneus Tertius.
- Lateral Compartment: Peroneus Brevis and Peroneus Longus.
- Posterior Compartment: Gastrocnemius, Plantaris, Soleus, Popliteus, Flexor Hallucis Longus, and Flexor Digitorum Longus.
General Ankle Biomechanics
Osteokinematics: a) Flexion (Dorsiflexion) b) Extension (Plantar Flexion)
Arthrokinematics: The talus slides on the tibial shroud (mortise).
- In Flexion (Dorsiflexion): Glides posteriorly.
- In Extension (Plantar Flexion): Glides anteriorly.
Relationship between the Peroneus and Talar Trochlea: [Incomplete thought in original text]
The Peritalar Joint Complex
The complex includes the following articulations:
- Talocrural (Tibiotalar)
- Subtalar
- Midtarsal
Talocrural Joint (Hinge Joint) Anatomy
Articulating Surfaces:
- Talus (Astragalus): Talar trochlea and medial/lateral facets. This is a unique articular surface covered by hyaline cartilage.
- Distal Epiphysis of the Tibia and Fibula (The Mortise).
Ankle Ligaments (Lateral and Medial)
External (Lateral) Ligaments: These resist inversion and internal rotation.
- Anterior Talofibular Ligament (ATFL): Stabilizes the ankle in the A/P plane, especially in 10º–20º of plantar flexion.
- Calcaneofibular Ligament (CFL): Stabilizes the joint against varus stress.
- Posterior Talofibular Ligament (PTFL).
Internal (Medial) Ligaments (Deltoid Complex): These resist eversion and external rotation.
- Tibionavicular Ligament
- Anterior and Posterior Tibiotalar Ligaments
- Tibiocalcaneal Ligament
Subtalar Joint (Plane/Arthrodiac Joint)
Articulating Surfaces:
- Talus: Concave posterior surface and anteroinferior surface (head and neck).
- Calcaneus: More convex anterior surface.
Passive Stabilizers
- Lateral Talocalcaneal Ligament
- Posterior Talocalcaneal Ligament
- Cervical Ligament
- Interosseous Ligament
Midtarsal Joint (Transverse Tarsal Joint)
This joint is composed of two distinct articulations:
- Talonavicular Joint: Plane joint (Arthrodiac) type.
- Calcaneocuboid Joint: Ball and socket joint type.
Passive Stabilizers
- Plantar Calcaneonavicular Ligament (Spring Ligament)
- Superior Talonavicular Ligament
- Chopart's Ligament (Bifurcate Ligament):
- Calcaneonavicular part
- Calcaneocuboid part
- Plantar Calcaneocuboid Ligament (Long Plantar Ligament)