The loss of normal medial longitudinal arch may arise as a consequence of hyper-pronation or from increased eversion of the subtalar joint (the calcaneus lies in valgus and external rotation relative to the talus). This situation may lead to pes planus, which can be flexible or rigid. This corroborates Magee’s observations.
Pes planus AKA flat feet or ‘fallen arches’ result from the collapse of the main arch of the foot – the medial longitudinal arch. A normal foot has an apparent arch while in a non-weight bearing position (e.g. sitting, lying) and also when they are in a weight bearing position (e.g. standing, walking, running).
There are two types of flat feet, rigid flat feet (RFF) and flexible flat feet (FFF). An individual with RFF has no arch at any time – either in a weight bearing position or in a non-weight bearing position. RFF is usually caused by some underlying pathology. A condition called tarsal coalition is the most common reason for RFF and occurs when two or more of the seven tarsal (foot) bones fuse together. Trauma, infection, neuromuscular and autoimmune disorders (such as Rheumatoid Arthritis) can also result in RFF.
An individual with an arch in a non-weight bearing position which fatigues or collapses in a weight bearing position such as standing or when the foot is stressed is said to have FFF. FFF is most often due to ligament laxity (the ligaments connecting the bones together have weakened) or due to muscle or tendon weakness.
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