Clubfoot can be classified as either of the following:
Postural or positional - Technically, these are not true clubfeet
In the past, clubfoot surgery was performed in a way that did not differentiate severity. The same procedure was performed for all patients. Bensahel proposed a more individualized approach (ie, addressing only the structures that are required are released), in which the surgery is tailored to the deformity. For example, if the forefoot is well corrected and externally rotated, if there is no cavus, but if there is still significant equinus, a posterior approach alone should suffice (see Treatment). 
Factors related to bone anatomy include the following:
Tibia - Slight shortening is possible
Fibula - Shortening is common
Talus - In equinus in the ankle mortise, with the body of the talus being in external rotation, the body of the talus is extruded anterolaterally and is uncovered and can be palpated; the neck of the talus is medially deviated and plantarflexed; all relations of the talus to the surrounding bones are abnormal
Os calcis - Medial rotation and an equinus and adduction deformity are present
Navicular - The navicular is medially subluxated over the talar head
Cuboid - The cuboid is medially subluxated over the calcaneal head
Forefoot - The forefoot is adducted and supinated; severe cases also have cavus with a dropped first metatarsal
Factors related to muscle anatomy include the following:
Atrophy of the leg muscles, especially in the peroneal group, is seen in clubfeet
The number of fibers in the muscles is normal, but the fibers are smaller
The triceps surae, tibialis posterior, flexor digitorum longus (FDL), and flexor hallucis longus (FHL) are contracted
The calf is smaller and remains so throughout life, even after successful long-lasting correction of the feet
Thickening of the tendon sheaths frequently is present, especially of the tibialis posterior and peroneal sheaths. Contractures of the posterior ankle capsule, subtalar capsule, and talonavicular and calcaneocuboid joint capsules commonly are seen. Contractures are seen in the calcaneofibular, talofibular, (ankle) deltoid, long and short plantar, spring, and bifurcate ligaments. The plantar fascial contracture contributes to the cavus, as does contracture of fascial planes in the foot.
Various theories of the pathogenesis of clubfeet have been advanced, including the following:
Arrest of fetal development in the fibular stage
Defective cartilaginous anlage of the talus
Anomalous tendon insertions
With respect to neurogenic factors, histochemical abnormalities have been found in posteromedial and peroneal muscle groups of patients with clubfeet. This is postulated to be due to innervation changes in intrauterine life secondary to a neurologic event, such as a stroke leading to mild hemiparesis or paraparesis. This is further supported by a 35% incidence of varus and equinovarus deformity in spina bifida.
Retracting fibrosis (or myofibrosis) may occur secondary to increased fibrous tissue in muscles and ligaments. In fetal and cadaveric studies, Ponseti also found the collagen in all of the ligamentous and tendinous structures (except the Achilles [calcaneal] tendon), and it was very loosely crimped and could be stretched. The Achilles tendon, on the other hand, was made up of tightly crimped collagen and was resistant to stretching. Zimny et al found myoblasts in medial fascia on electron microscopy and postulated that they cause medial contracture. [1, 2, 8]
Inclan proposed that anomalous tendon insertions result in clubfeet.  However, other studies have not supported this proposal. It is more likely that the distorted clubfoot anatomy can make it appear that tendon insertions are anomalous.
Robertson noted seasonal variations to be a factor in his epidemiologic studies in developing countries.  This coincided with a similar variation in the incidence of poliomyelitis in the children in the community. Clubfoot was therefore proposed to be a sequela of a prenatal poliolike condition. This theory is further supported by motor neuron changes in the anterior horn in the spinal cord of these babies.
The true etiology of congenital clubfoot is unknown. Most infants who have clubfoot have no identifiable genetic, syndromal, or extrinsic cause. 
Extrinsic associations include teratogenic agents (eg, sodium aminopterin), oligohydramnios, and congenital constriction rings. Genetic associations include mendelian inheritance (eg, diastrophic dwarfism; autosomal recessive pattern of clubfoot inheritance).
Cytogenetic abnormalities (eg, congenital talipes equinovarus [CTEV]) can be seen in syndromes involving chromosomal deletion. It has been proposed that idiopathic CTEV in otherwise healthy infants is the result of a multifactorial system of inheritance.  Evidence for this is as follows:
Incidence in the general population is 1 per 1000 live births
Incidence in first-degree relations is approximately 2%
Incidence in second-degree relations is approximately 0.6%
If one monozygotic twin has a CTEV, the second twin has only a 32% chance of having a CTEV
A study by Weymouth et al found that associated promoter variants in HOXA9, TPM1, and TPM2 alter promoter expression suggesting that they have a functional role in gene regulation in clubfoot. 
The incidence of clubfoot is approximately 1 case per 1000 live births in the United States. The incidence differs among ethnicities. For example, it is close to 75 cases per 1000 live births in the Polynesian islands, particularly in Tonga.
The male-to-female ratio has been reported to be 2:1. Bilateral involvement is found in 30-50% of cases. A 2017 study by Zionts et al found that severity did not differ significantly by either sex or bilaterality, though patients with bilateral clubfoot had a wider range of severity. 
There is a 10% chance of a subsequent child being affected if the parents already have a child with a clubfoot.
Parker et al pooled data from several birth defects surveillance programs (6139 cases of clubfoot) to better estimate the prevalence of clubfoot and investigate its risk factors.  The overall prevalence of clubfoot was 1.29 per 1000 live births, with figures of 1.38 among non-Hispanic whites, 1.30 among Hispanics, and 1.14 among non-Hispanic blacks or African Americans. Maternal age, parity, education, and marital status were significantly associated with clubfoot, along with maternal smoking and diabetes.
Approximately 50% of clubfeet in newborns can be corrected nonoperatively. Ponseti has reported an 89% success rate using his technique (including an Achilles tenotomy); others have reported success rates of 10-35%. One study analyzed the correction progression of patients with idiopathic clubfeet after the Ponseti technique.  The data indicated that successive castings resulted in reduced cavus and medial crease with a gradual correction of midfoot rotation, adduction, and heel varus. Interestingly, heel equinus improved concurrent with midfoot variables and also with final casting.
Most series report 75-90% satisfactory results of operative treatment (appearance and function of the foot). The amount of motion in the joints of the foot and ankle correlates with the degree of patient satisfaction. [16, 17, 18]
Satisfactory results were obtained in 81% of cases, and the range of ankle movement was a major factor in determining the functional result, which again was influenced by the degree of talar dome flattening (suggesting that the primary bone deformity present at birth dictates the eventual result of treatment). In all, 44% of patients had no dorsiflexion beyond neutral, and 38% of patients required further surgery (nearly two thirds of these were bony procedures).
The best results were obtained with children older than 3-4 months with a foot large enough to allow the procedure to be performed without compromise (longer than 8 cm, as specified by Simons [21, 22] ). The age at operation is directly related to the result. Less-than-satisfactory results may be associated with overcorrection, which occurs in approximately 15% of cases.
Previous surgery seems to have a deleterious effect on the result.
Steinman et al compared the Ponseti and French functional methods for idiopathic clubfeet (265 feet [176 patients] by the Ponseti method; 119 feet [80 patients] by the French functional method).  The study showed that although there was a trend toward improved results with the Ponseti method, the difference was not significant. Parents chose the Ponseti method twice as often as the French functional method. Initial correction rates were 94.4% for the Ponseti method and 95% for the French functional method.
Relapses occurred in 37% of the Ponseti-method feet, and in a third of these cases, further nonoperative treatment was successful; however, surgical treatment was necessary for the other two thirds.  Relapses occurred in 29% of the feet treated by the French functional method; surgical intervention was necessary in all those cases. At the latest follow-up, outcomes with the Ponseti method were good in 72% of cases, fair in 12%, and poor in 16%. For the French functional method, outcomes were good in 67%,fair in17%,and poor in 16%.
In a controlled study of 164 patients (238 feet), Jeans et al compared the Ponseti method (n=122) with the French physiotherapy (PT) method (n=116) in terms of pedobarographic findings at age 5 years.  The only significant difference noted between the two groups was that the PT group had significantly less medial movement of the center of pressure (COP) line. Plantar pressures in the hindfoot and first metatarsal regions were decreased in both groups as compared with control subjects and increased in the midfoot and lateral forefoot regions. Mild residual deformity remained even though clinically successful outcomes were achieved.
Parada et al reviewed the safety of general anesthesia in infants who underwent percutaneous tendoachilles tenotomy. The procedure was performed in 137 patients (182 tenotomies). Of the tenotomies, 92 were unilateral and 45 bilateral. No complications related to anesthesia were identified, and nearly all patients were discharged on the day of surgery. 
Pavone et al achieved good/excellent outcomes in 96% of the 82 patients with 114 congenital clubfeet treated with the Ponseti method from 2004 through 2010, with follow-up through 2011. 
A two-institution review by Miller et al found that strict adherence to the Ponseti method in nonoperative treatment of isolated clubfoot, as opposed to more flexible adherence, was associated with improved outcome in the form of a reduced risk of subsequent unplanned surgical intervention. 
In a cross-sectional study of postcorrection brace wear over a 3-month period in 48 patients in four age-based groups (6-12 months, >1 to 2 years, >2 to 3 years, and >3 to 4 years) who were treated for idiopathic clubfoot, Sangiorgio et al found that patients who wore the brace for a mean of 8 hours daily had significantly lower relapse rates than those whe wore the brace for a mean of 5 hours daily.