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lateral Talocrural joint • inferior tibiofibular jnt. • tibiotalar jnt. Subtalar joint • aka talocalcaneal • between talus and calcaneus Midtarsal joint • between calcaneus and cuboid on lateral side medial • between talus and navicular on the medial side Talocrural Joint • Articulation between the tibia and fibula (inferior tibiofibular joint) and between the tibia and the talus (tibiotalar joint). • This joint is responsible for plantar flexion and dorsiflexion and some abduction/adduction. • The axis of rotation is a line between the two malleoli. Subtalar Joint • Allows pronation/supination and rotation. • The talus articulates with the calcaneus anteriorly, posteriorly and medially. • The axis of rotation runs diagonally from the posterior, lateral, plantar surface to the anterior, medial, dorsal surface. • The orientation of this axis makes pronation/supination triplanar with reference to the cardinal planes. Pronation/Supination Open Chain calcaneus moves on talus Closed Chain talus moves on calcaneus Pronation Supination calcaneal eversion abduction dorsiflexion calcaneal inversion adduction plantar flexion calcaneal eversion talar adduction plantar flexion calcaneal inversion talar abduction dorsiflexion Tibial Rotation It is important that knee flexion and pronation occur in synchronization (as well as knee extension and supination). • The subtalar joint can be likened to the action of a mitered hinge (Inman and Mann, 1973). • The orientation of the subtalar joint axis causes the tibia to internally rotate during pronation and externally rotate during supination. • Thus, the tibia internally rotates with pronation or knee flexion and externally rotates with supination or knee extension. Midtarsal Joint Actually consists of two joints: the calcaneocuboid on the lateral side and the talonavicular on the medial side. During pronation, the axes of these two joints are parallel, this unlocks the joint and creates a hypermobile foot that can absorb shock. During supination the axes are not parallel and this joint becomes locked allowing efficient transmission of forces. Foot Orientation A forefoot valgus exists when the forefoot is everted relative the rearfoot. This is not as common as forefoot varus. A forefoot varus exists when the forefoot is inverted to the rearfoot. This is the most common cause of excessive pronation. A rearfoot valgus exists when the rearfoot is everted. A rearfoot varus exists when the rearfoot is inverted. This can increase maximum pronation. Ligaments Lateral side of ankle accounts for 85% of ankle sprains Arches of the Foot Fascia Plantar surface There are 3 arches in the foot that contribute to support and shock absorption. These arches are maintained by the shape of the tarsal and metatarsal bones, ligaments and plantar fascia. Arch Types • Feet are often classified according to the height of the medial arch. – Normal – high-arched or pes cavus – flat-footed or pes planus • Arches can also be rigid or flexible. • High-arched, rigid feet make poor shock absorbers. • Flat-footed, flexible arches often allow excessive pronation. Plantar Flexors Gastrocnemius NOTE: 1) Soleus lies deep to gastrocnemius 2) Both insert into the calcaneal tendon aka Achilles tendon Posterior View Soleus Assistant Plantar Flexors Tibialis Peroneus Posterior Brevis Peroneus Longus Note: Their tendons pass posteriorly to the malleoli Flexor Flexor Digitorum Hallucis Longus Longus Plantaris Note: insertion is wrong! Dorsiflexion tibialis anterior extensor digitorum longus peroneus tertius (usually very close to extensor digitorum longus and often considered as part of this muscle) extensor hallucis longus (deep to ext. digitorum longus) Invertors primary tibialis anterior tibialis posterior extensor hallucis longus NOTE: Muscles pass to the medial side of the foot! flexor flexor digitorum hallucis longus longus Evertors primary peroneus brevis peroneus longus peroneus tertius extensor digitorum longus Causes of Excessive Pronation • • • • • • • Q-angle greater than 20 degrees tibial varus greater than 5 degrees rearfoot varus greater than 2 degrees forefoot varus greater than 3 degrees plantar flexed first ray weak medial arch tight gastrocnemius and soleus or a short Achilles tendon The Problem with Excessive Pronation Excessive or prolonged pronation during the support phase will disrupt the normal tibial-femoral rotation relationship at the knee. The tibia continues to internally rotate with the prolonged pronation while the knee is extending. Knee extension is normally associated with external tibial rotation.
