Clubfoot is caused by a combination of genetic, environmental, and neuromuscular factors, though in most cases no single cause can be pinpointed. Roughly 80% of cases are classified as “idiopathic,” meaning they arise without a clear underlying condition. The remaining 20% are linked to specific syndromes, chromosomal abnormalities, or nervous system disorders. About 1.18 in every 1,000 babies are born with clubfoot worldwide, which adds up to an estimated 176,000 children each year.
Genetics Play a Central Role
Family history is one of the strongest predictors of clubfoot. If a parent or sibling was born with the condition, the chances of it recurring in a future child rise significantly. Researchers have identified a specific genetic pathway involving two genes, PITX1 and TBX4, as the most strongly associated with the malformation. Both genes are essential for normal hindlimb development in the embryo. Mutations in PITX1 follow a dominant inheritance pattern, meaning a single altered copy from one parent can be enough to produce the clubfoot deformity. Deletions and duplications of small segments involving TBX4 have also been found in affected children.
These genetic findings help explain why clubfoot runs in families, but they don’t account for every case. Many children born with clubfoot have no family history at all, which points to other contributing factors or new spontaneous mutations.
Smoking During Pregnancy and Other Risk Factors
Maternal smoking during pregnancy is the only common environmental factor that has been consistently shown to increase the risk for clubfoot. Studies estimate the relative risk at roughly 1.3 to 2.6 times higher for mothers who smoke compared to those who don’t. That range depends on how much a mother smokes and other individual factors.
The risk jumps dramatically when smoking combines with a family history of clubfoot. In families where the condition has already occurred, a mother who smokes during pregnancy faces about a 20-fold increase in risk. That interaction between genes and environment is one of the clearest examples in clubfoot research: neither factor alone fully explains the condition, but together they multiply each other’s effects.
Boys are affected more often than girls, and firstborn children appear to have a slightly higher prevalence, though the reasons for both patterns remain unclear.
Low Amniotic Fluid and Uterine Crowding
One of the oldest theories about clubfoot involves physical restriction inside the womb. The idea is straightforward: if a developing foot can’t move freely, it may get stuck in the characteristic downward-and-inward position. Low amniotic fluid (oligohydramnios) can create this kind of cramped environment.
There is some supporting evidence. In studies of early amniocentesis, where a needle is used to withdraw fluid for testing, amniotic fluid leakage afterward was associated with a much higher clubfoot rate: 15% of pregnancies with fluid leakage resulted in clubfoot, compared to just 1.1% without leakage. Interestingly, the timing seems to matter. There may be a critical window around 11 to 12 weeks of gestation when the developing foot is especially vulnerable to restricted movement. The mildest cases of clubfoot do appear to be linked to positioning in the uterus, though severe cases likely have deeper biological roots.
Neuromuscular and Vascular Theories
Clubfoot likely represents what researchers call a “final common pathway,” meaning many different problems along the chain from brain to spinal cord to nerve to muscle can all produce the same deformity at the foot. This helps explain why the condition looks the same whether it’s caused by a genetic mutation, a nerve disorder, or restricted fetal movement.
Some researchers have focused on abnormal muscle development in the lower leg. Babies with clubfoot often have smaller, differently structured calf muscles on the affected side, and some studies have found unusual placement of muscle attachments around the foot and ankle. Others have investigated whether reduced blood flow to the developing foot could interfere with normal growth. Both the muscle-based and blood-supply-based theories have some laboratory support, but neither has been confirmed as a standalone explanation for idiopathic cases.
When Clubfoot Is Part of a Larger Condition
About one in five cases of clubfoot occurs alongside another condition. Arthrogryposis, a group of disorders that cause joint stiffness throughout the body, is one of the most common syndromic causes. Myelomeningocele, the most severe form of spina bifida, is another frequent association. In myelomeningocele, the spinal cord doesn’t close properly during early development, which disrupts nerve signals to the legs and feet.
More broadly, disorders involving the nervous system account for the greatest number of known, identifiable causes of clubfoot. This includes conditions affecting the brain, spinal cord, or peripheral nerves. Many other genetic syndromes beyond arthrogryposis also feature clubfoot as one of several symptoms. When clubfoot appears alongside other physical differences or developmental concerns, doctors typically investigate whether a broader syndrome is involved, since management may differ.
When Clubfoot Can Be Detected
Most cases are spotted on a prenatal ultrasound before birth. About 10% of clubfeet can be identified as early as 13 weeks into pregnancy. By 24 weeks, roughly 80% are detectable, and the number continues to climb through the rest of pregnancy. A prenatal diagnosis gives families time to connect with a pediatric orthopedic specialist and plan for treatment, which typically begins within the first few weeks of life. Cases that aren’t caught on ultrasound are identified immediately at birth through a physical exam.