Pes cavus, commonly known as high-arched foot or cavus foot, is a structural deformity characterized by an abnormally elevated longitudinal arch of the foot. This condition affects the foot’s biomechanics, often leading to pain, instability, and secondary complications such as claw toes, calluses, or ankle sprains. While pes cavus can be asymptomatic in mild cases, severe forms may require orthotic interventions, physical therapy, or surgery. Estimates suggest that pes cavus occurs in approximately 8-15% of the population, with varying degrees of severity. Understanding its causes is crucial for effective diagnosis and management, as the etiology influences whether the deformity is progressive or static.
Pes cavus is not a monolithic condition but can be classified based on anatomical presentation and driving factors. The most common variant is pes cavovarus, where the high arch (cavus) combines with an inward-tilting heel (varus) and a downward-flexed big toe, creating a claw-like appearance. This form often stems from neuromuscular imbalances and is progressive if untreated. In contrast, pes calcaneocavus features a dorsiflexed heel (calcaneus) and a plantarflexed forefoot, resulting in the highest arch at the rear of the foot; this is less common and typically linked to conditions like poliomyelitis. A third type, pure pes cavus, involves a neutral heel position with the elevation confined to the forefoot, often seen in idiopathic cases. Additionally, classifications distinguish between forefoot-driven (where the first ray is plantarflexed) and hindfoot-driven (varus malalignment) deformities, as well as flexible versus rigid forms based on whether the arch can be corrected manually. These distinctions are essential because they guide treatment; for instance, forefoot-driven cases may respond better to orthotics, while hindfoot-driven ones might necessitate surgical realignment.
The primary causes of pes cavus are multifaceted, broadly categorized into neurological, traumatic, congenital, idiopathic, and other miscellaneous factors. Neurological disorders account for the majority of cases, particularly in adults where two-thirds of symptomatic presentations involve an underlying neurologic condition. Hereditary motor and sensory neuropathies (HMSNs), such as Charcot-Marie-Tooth (CMT) disease, are the most prevalent culprits. CMT, a genetically heterogeneous disorder, leads to progressive degeneration of peripheral nerve myelin, causing distal muscle weakness and sensory loss. It typically manifests in childhood with delayed motor milestones, clumsiness, and falls, evolving into painful foot deformities by adulthood. Other hereditary neurological causes include Friedreich’s ataxia, which affects coordination and balance due to spinal cord and peripheral nerve degeneration; spinal muscular atrophy, involving motor neuron loss; and hereditary spastic paraplegia, characterized by progressive leg stiffness and weakness.
Non-hereditary neurological conditions also contribute significantly. Cerebral palsy, resulting from brain injury during development, can cause spasticity that distorts foot architecture, leading to various cavus shapes. Spina bifida, a congenital neural tube defect, disrupts nerve function to the lower extremities, often resulting in muscle imbalances. Poliomyelitis, though rare in developed countries due to vaccination, historically caused pes calcaneocavus through paralysis of the calf muscles (gastrocnemius-soleus complex). More severe conditions like syringomyelia (a cyst in the spinal cord), intraspinal tumors, anterior horn disease, amyotrophic lateral sclerosis (ALS), Parkinson disease, Huntington chorea, and leprosy can induce similar imbalances by affecting motor neurons or peripheral nerves. Unilateral pes cavus without trauma may signal a spinal tumor, warranting immediate imaging. These neurological etiologies underscore the importance of a thorough neurologic evaluation in patients presenting with high arches, as early intervention can mitigate progression.
Traumatic causes represent another key category, often leading to hindfoot-driven deformities. Malunion of fractures, particularly in the calcaneus (heel bone) or talus (ankle bone), can alter foot alignment, forcing compensatory arch elevation. For example, a malunited talar neck fracture may cause varus deformity, while distal tibial fractures or pilon fractures (involving the ankle joint) can lead to similar outcomes. Compartment syndrome, a condition where increased pressure in muscle compartments impairs blood flow, often follows trauma like crush injuries and can result in muscle necrosis and contractures that pull the foot into a cavus position. Burns, especially those affecting the lower leg, cause scar tissue formation and contractures, restricting normal foot motion. Peroneal nerve injury, knee dislocation, or vascular lesions from trauma can weaken specific muscles, such as the peroneus brevis, exacerbating imbalances. Hindfoot instability from longstanding ankle sprains may also progress to fixed varus, highlighting how acute injuries can evolve into chronic deformities if not properly managed.
Congenital and idiopathic causes round out the spectrum. Congenital clubfoot (talipes equinovarus), if untreated or inadequately treated, can leave residual high arches due to persistent muscle contractures from intrauterine positioning. Tarsal coalition, a congenital fusion of foot bones, restricts motion and may contribute to cavus. Idiopathic pes cavus, accounting for about 20% of cases, has no identifiable cause and is often nonprogressive, though it may have subtle genetic underpinnings with unclear inheritance patterns. In these instances, the foot may function as an underpronator, leading to lateral overload and secondary issues like peroneal tendon pathology or ankle arthritis.
Miscellaneous causes include rheumatoid arthritis, which inflames joints and alters foot structure; ankle osteoarthritis, causing compensatory changes; plantar fibromatosis (thickening of the plantar fascia); diabetic foot syndrome, involving neuropathy and muscle atrophy; and even rare syndromes like CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, sensorineural hearing loss) due to ATP1A3 gene mutations.
At the mechanistic level, pes cavus develops primarily through muscle imbalances that disrupt the foot’s normal architecture. In forefoot-driven cases, weak muscles like the tibialis anterior and peroneus brevis are overpowered by antagonists such as the peroneus longus and tibialis posterior. The peroneus longus plantarflexes the first ray, pronating the forefoot, while the tibialis posterior inverts the subtalar joint. This forces the hindfoot into varus for stability, shortening the Achilles tendon and tightening the plantar fascia, which reduces shock absorption. In CMT, this agonist-antagonist dynamic is pronounced, with intrinsic muscle contractures leading to claw toes and increased lateral ankle stress. Hindfoot-driven mechanisms, often traumatic, involve varus from instability or malunion, with the subtalar joint compensating until fixed. If imbalances occur before skeletal maturity, bone morphology changes profoundly; post-maturity, changes are subtler. Overall, these mechanisms emphasize the interplay between neurology, trauma, and biomechanics in pes cavus pathogenesis.
Pes cavus arises from a diverse array of causes, predominantly neurological like CMT, but also traumatic, congenital, and idiopathic. Classifications such as cavovarus and calcaneocavus highlight the deformity’s variability, while mechanisms rooted in muscle imbalances explain its development. Early identification of the underlying cause is vital, as it informs prognosis and treatment, potentially preventing complications like chronic pain or mobility loss. Future research into genetic therapies for hereditary forms may offer new hope, but for now, a multidisciplinary approach remains key to managing this complex condition.