Sunday, January 10, 2010

Ankle joint biomechanical pearls


Ankle joint = tibio-talar joint, permits DF & PF

Dorsiflexion (DF) is performed by the tibialis anterior , EHL,EDL,and peroneus tertius.

DF limited by the tension of the tendocalcaneus , the posterior fibers of the medial ligament and the calcaneofibular ligament.
During dorsiflexion the wider anterior part of the articular surface of the talus is forced between the medial & lateral malleolus, causing them to separate slightly & tighten the ligaments of the distal tibiofibular joint.
This arrangement increases the stability of the ankle joint when the foot is in the initial position for major thrusting movements in running , jumping and walk .

Plantar flexion is performed by the gastrocnemius, soleus,plantaris, peroneus longus & brevis , tibialis posterior, flexor digitorum longus and flexor hallucis longus

It is limited by the tension of the opposing muscles , the anterior fibers of the medial ligament and the anterior talofibular ligament .

When the ankle is fully plantar flexed, the ligaments of the distal tibiofibular joint are less taut and small amounts of rotation , abduction & adduction are possible.

Tarsal joints that produce Inversion & eversion

1- Subtalar joint
It is between the inferior surface of the body of the talus and the facet on the middle of the upper surface of the calcaneum.
2- Talocalcaneonavicular joint
It is between the rounded head of the talus , the upper surface of the sustentaculum tali and the posterior concave surface of the navicular bone.
3- Calcaneocuboid joint
It is between the anterior end of the calcaneum & the posterior surface of the cuboid .
The talocalcaneonavicular & calcaneo-cuboid joints are together referred as midtarsal or transverse tarsal joints .
N.B. The inversion & eversion movements take place at the 3 previous joints.



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