As we walk the foot strikes the ground slightly on the outer side of the heel. Turning forces encourage the foot to roll towards the inner side. This natural movement causes the inner arch to lower and the heel to lean inwards. This movement is called pronation. In some feet this leaning of the heel is excessive and can cause strain on supportive ligaments and joints of the foot; notably the calcaneo-cuboid and talonavicular joints (midtarsal joint). Supportive posture is lost, painful symptoms develop in the foot or ankle and leg (due to associated internal leg rotation). Lower back symptoms and loss of core stability may occur. In order to prevent this from occurring the heel should remain vertical, the medial arch must be supported and pressure through the forefoot should be evenly distributed.
The majority of sumptoms caused by poor foot posture result from excessive valgus rotation of the heel. This occurs as a consequence of pronation. Whilst different foot types manifest pronation in a number of different ways the most common associated finding is failure of the heel to recover from this valgus position. The TRIO range of foot orthotics is designed to correct this and thus restore the body`s natural ability to pronate normally and recover itself to provide mid tarsal joint stability and correct foot function.
The TRIO orthotic is designed to resist excessive valgus rotation. It does this by inverting the calcaneus within the heel cup. In this way mid tarsal joint integrity is maintained and damaging compensations are avoided. TRIO also supports the proximal medial arch of the foot providing navicular stability. It is essential to allow for the first MTP joint to extend during propulsion. TRIO is designed to facilitate this by means of a cushioned recess for the first ray. Inverted (varus) orientation of the forefoot may be treated by using the medial forefoot post to replace the Poron infill under the first MTP joint. Alternatively propulsion through the hallux can be encouraged by using the forefoot lateral post where necessary. Only one of these forefoot posts should be used on each device. if symptoms fail to respond it is possible to increase subtalar joint control by applying the additional biplanar rearfoot post to the demarcated area on the underside of the orthotic. This provides further extrinsic posting control.