and occasionally idiopathic. (See CMT Association website) There are many different types and subtypes of CMT, and as a result, it can present from infancy through to adulthood. CMT is a peripheral neuropathy, affecting the distal muscles first as weakness, clumsiness, and frequent falls. It usually affects the feet first, but can sometimes begin in the hands. Charcot-Marie-Tooth disease can cause painful foot deformities such as pes cavus. Although it is a relatively common disease, many doctors and laypersons are not familiar with it. There are no cures or effective courses of treatment to halt the progression of any form of Charcot-Marie-Tooth disease at this time. The development of the cavus foot structure seen in Charcot-Marie-Tooth disease has been previously linked to an imbalance of muscle strength around the foot and ankle. A hypothetical model proposed by various authors describes a relationship whereby weak evertor muscles are overpowered by stronger invertor muscles, causing an adducted forefoot and inverted rearfoot. Similarly, weak dorsiflexors are overpowered by stronger plantarflexors, causing a plantarflexed first metatarsal and anterior pes cavus. Pes cavus is also evident in people without neuropathy or other neurological deficit. In the absence of neurological, congenital, or traumatic causes of pes cavus, the remaining cases are classified as being ‘idiopathic’ because their aetiology is unknown. Diagnosis On weightbearing projectional radiography, pes cavus can be diagnosed and graded by several features, the most important being medial peritalar subluxation, increased calcaneal pitch (variable) and abnormal talar-1st metatarsal angle (Meary's angle). Medial peritalar subluxation can be demonstrated by a medially rotated talonavicular coverage angle. Types The term pes cavus encompasses a broad spectrum of foot deformities. Three main types of pes cavus are regularly described in the literature: pes cavovarus, pes calcaneocavus, and ‘pure’ pes cavus. The three types of pes cavus can be distinguished by their aetiology, clinical signs and radiological appearance. Pes cavovarus, the most common type of pes cavus, is seen primarily in neuromuscular disorders such as Charcot-Marie-Tooth disease and, in cases of unknown aetiology, is conventionally termed ‘idiopathic’. Pes cavovarus presents with the calcaneus in varus, the first metatarsal plantarflexed, and a claw-toe deformity. Radiological analysis of pes cavus in Charcot-Marie-Tooth disease shows the forefoot is typically plantarflexed in relation to the rearfoot. In the pes calcaneocavus foot, which is seen primarily following paralysis of the triceps surae due to poliomyelitis, the calcaneus is dorsiflexed and the forefoot is plantarflexed.