Pes planus, commonly known as flatfoot, describes a condition where the arch on the inner side of the foot collapses, causing the entire sole to contact the ground. While flat feet are common in infants, the term congenital pes planus refers specifically to a structural abnormality present from birth. This condition is distinct from the flexible flat foot that most toddlers possess and eventually outgrow, representing a fixed deformity that may lead to pain, altered walking patterns, and functional limitations.
Defining Congenital Pes Planus
Congenital pes planus is characterized by a foot that remains flat regardless of whether the person is standing or sitting, defining it as a “rigid” flatfoot. The constant lack of a medial longitudinal arch indicates a fixed structural problem within the foot’s skeletal or joint alignment. This rigidity is the key functional difference from a flexible flat foot, where the arch reappears when the foot is non-weight-bearing, such as when standing on tiptoes.
The anatomical presentation often includes a heel that is pronated, or angled outward, known as hindfoot valgus. This misalignment causes the ankle to appear as if it is rolling inward and can be associated with the forefoot pointing outward. Unlike the flexible type, which is often asymptomatic, congenital rigid flatfoot can lead to pain in the arch, heel, or ankle, and generalized foot fatigue. Over time, the altered mechanics can affect the entire lower limb alignment, contributing to pain in the knee, hip, and lower back.
Etiology and Contributing Factors
The underlying causes of congenital rigid flatfoot are structural malformations affecting the joints and bones of the mid- and hindfoot that occur during fetal development. One frequent cause is Tarsal Coalition, a condition where two or more tarsal bones in the back of the foot fail to fully separate. This incomplete differentiation results in a fibrous, cartilaginous, or bony bridge forming between bones, such as the calcaneus and the navicular, or the talus and the calcaneus.
This coalition restricts the normal motion between the foot bones, causing the foot’s characteristic rigidity. Symptoms often become apparent in later childhood or early adolescence, typically between the ages of 8 and 16, as the cartilaginous connections begin to ossify, or harden into bone. Another, less common but more severe cause is Congenital Vertical Talus, where the talus bone is malpositioned, fixed in a vertical orientation, and the navicular bone is dislocated dorsally. This deformity creates a rocker-bottom appearance to the foot, which is present at birth and severely limits foot mobility.
Clinical Assessment and Diagnostic Tools
The diagnostic process begins with a thorough physical examination to differentiate a rigid flatfoot from the more common flexible type. A physician observes the foot both when the patient is standing and when they are sitting or lying down. A crucial test is the “tip-toe test,” where the patient stands on their toes; a flexible arch will temporarily reappear during this maneuver, while a rigid one will not.
The physician also assesses the mobility of the hindfoot, checking for restricted movement, especially during passive inversion and eversion. Imaging studies confirm the diagnosis and identify the anatomical cause of the rigidity. Standard weight-bearing X-rays are the first step, providing views of the foot bones under stress necessary for accurate assessment of arch collapse and alignment. These images help visualize the Meary’s angle, a measurement that quantifies the degree of pes planus. If a tarsal coalition is suspected, specialized views or advanced imaging like Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) may be ordered for a clearer view of bone connections and soft tissue structures.
Management and Treatment Options
Treatment for congenital rigid flatfoot is determined by the severity of the deformity, the presence of pain, and the underlying cause. Conservative management is often the first approach for symptomatic but non-progressive cases, focusing on managing discomfort. This includes the use of custom-molded foot orthotics or shoe inserts, which support the fallen arch and improve the alignment of the foot and ankle.
Physical therapy can be beneficial, focusing on strengthening the muscles that support the arch, such as the posterior tibialis tendon, and stretching a tight Achilles tendon. Activity modification may also be recommended to reduce pain during high-impact sports. If conservative measures fail to relieve disabling pain, or if the deformity is severe and progressive, surgical intervention may be considered. Procedures can involve the resection of a bony or cartilaginous tarsal coalition to restore motion, or complex reconstructions to correct a vertical talus. The goal of surgery is to achieve pain relief and improve the functional mechanics of the foot.