What Causes Bilateral Clubfoot?
When a baby is diagnosed with bilateral clubfoot — meaning both feet are affected — parents naturally want to understand why. What causes bilateral clubfoot? Is it different from unilateral clubfoot (where only one foot is affected)? Does it suggest a more serious underlying condition? These are all valid questions, and this guide aims to answer them thoroughly, drawing on current medical research and NHS clinical guidelines.
Bilateral clubfoot accounts for approximately 50% of all clubfoot cases. In the UK, where clubfoot affects around 1 in 1,000 births, that means roughly 350-400 babies are born each year with both feet turned inwards. Understanding what causes this condition — and what doesn't — can help reduce anxiety and prepare you for the treatment experience ahead.
Understanding Clubfoot: The Basics
Clubfoot (congenital talipes equinovarus, or CTEV) is a condition where the foot is turned inwards and downwards at birth. The four components of the deformity are equinus (foot pointing down), varus (heel turning in), adduction (front of foot curving in), and cavus (high arch). In bilateral clubfoot, these features are present in both feet, though the severity may differ between them.
For a comprehensive overview of clubfoot causes in general, see our guide on what causes clubfoot. This article focuses specifically on why both feet can be affected and what that means for your baby.
Idiopathic Bilateral Clubfoot: The Most Common Type
In approximately 80% of bilateral clubfoot cases, the condition is idiopathic — meaning it occurs without any identifiable underlying cause. This is the same proportion as in unilateral clubfoot. Idiopathic clubfoot is the most common form and generally has the best outcomes with treatment.
The Multifactorial Theory
Current medical understanding suggests that idiopathic clubfoot — whether unilateral or bilateral — results from a combination of genetic and environmental factors acting together during early pregnancy. No single gene or environmental exposure has been identified as "the" cause. Instead, it's thought to be a complex interaction of multiple small factors that, together, disrupt normal foot development.
Key research findings include:
- Genetic contribution: Studies of twins show that if one identical twin has clubfoot, there is a 33% chance the other twin will too — compared with only 3% for non-identical twins. This strongly suggests a genetic component but not a simple single-gene inheritance pattern
- Family history: Having a first-degree relative (parent or sibling) with clubfoot increases the risk by approximately 20-30 times. Families with a history of clubfoot are more likely to have bilateral cases
- Multiple genes involved: Research has identified several genes potentially involved in clubfoot, including those related to limb development (PITX1, TBX4), muscle development, and connective tissue formation
For more on the genetic aspects, see our article on whether clubfoot is genetic or hereditary.
Why Both Feet? The Bilateral Question
If clubfoot is caused by a combination of genetic and environmental factors, why does it affect both feet in some babies and only one foot in others? This is an active area of research, and several theories have been proposed:
Threshold Model
One leading theory suggests a threshold model of causation. In this model, every baby has some level of susceptibility to clubfoot based on their genetic makeup. Environmental factors during pregnancy then push the overall risk higher or lower. When the combined genetic and environmental risk crosses a certain threshold, clubfoot develops.
In bilateral cases, the overall risk level may be higher — either because the genetic susceptibility is greater, or because the environmental factors were more pronounced — causing both feet to be affected rather than just one.
Systemic vs Local Factors
Another theory distinguishes between systemic factors (affecting the whole body) and local factors (affecting a specific area). Systemic factors — such as genetic predisposition, hormonal influences, or circulating growth factors — would tend to affect both feet equally, potentially leading to bilateral clubfoot. Local factors — such as the position of a specific foot in the uterus or localised vascular changes — might affect only one foot, leading to unilateral clubfoot.
Intrauterine Environment
The position of the baby in the womb has been proposed as a contributing factor, though this is more strongly associated with positional talipes than true structural clubfoot. Conditions that restrict foetal movement — such as oligohydramnios (low amniotic fluid) or a bicornuate uterus — could theoretically compress both feet into an abnormal position, contributing to bilateral clubfoot.
However, it's important to stress that most bilateral clubfoot occurs in pregnancies with completely normal amniotic fluid levels and uterine anatomy. Intrauterine positioning is, at most, one contributing factor among many.
Associated Conditions and Syndromic Clubfoot
While most bilateral clubfoot is idiopathic, bilateral presentation is slightly more likely to be associated with an underlying condition than unilateral clubfoot. This is why, when bilateral clubfoot is diagnosed, the medical team will often perform a more thorough assessment to check for associated conditions.
Conditions Sometimes Associated with Bilateral Clubfoot
- Arthrogryposis multiplex congenita (AMC): A condition causing multiple joint contractures throughout the body. Bilateral clubfoot is common in AMC and may be more resistant to standard Ponseti treatment
- Spina bifida: Neural tube defects can cause clubfoot due to disrupted nerve supply to the developing feet. Bilateral involvement is common
- Chromosomal conditions: Trisomy 18 (Edwards syndrome) and some other chromosomal abnormalities can include bilateral clubfoot as one of several features
- Myotonic dystrophy: This inherited muscle condition can cause clubfoot, typically bilateral
- Congenital myopathies: Various inherited muscle disorders may present with bilateral clubfoot
- Amniotic band syndrome: In rare cases, fibrous bands within the amniotic sac can compress the feet
It's crucial to emphasise that the vast majority of babies with bilateral clubfoot have no other medical conditions. The presence of bilateral clubfoot alone does not mean your baby has a syndrome — it's simply that the medical team will want to do a thorough check to make sure.
What Assessments Will Be Done?
When bilateral clubfoot is diagnosed — whether prenatally or at birth — you can expect:
- Detailed physical examination — checking all joints, muscle tone, spine, and overall development
- Hip ultrasound — developmental dysplasia of the hip (DDH) is slightly more common in babies with clubfoot
- Possible genetic testing — if there are other findings suggesting a syndromic cause. This might include a chromosomal microarray or specific genetic tests
- Spinal ultrasound — to look for spinal cord abnormalities if there are any concerns
If all these assessments are normal, the clubfoot is classified as idiopathic, and treatment proceeds with the standard Ponseti method.
Known Risk Factors for Bilateral Clubfoot
Research has identified several factors that may increase the likelihood of bilateral rather than unilateral clubfoot:
Family History
A positive family history of clubfoot is more commonly seen in bilateral cases than unilateral. This supports the idea that a stronger genetic predisposition leads to both feet being affected. If you or your partner had clubfoot, your child's risk is higher, and bilateral involvement is more likely (though still far from certain).
Sex
Clubfoot is approximately twice as common in boys as in girls. Interestingly, when girls do develop clubfoot, it is more likely to be bilateral. This observation fits with the threshold model — since girls are generally less susceptible, those who do develop clubfoot may have a higher overall risk load, which manifests as bilateral involvement. Read more about why clubfoot is more common in boys.
Smoking During Pregnancy
Maternal smoking has been consistently identified as a risk factor for clubfoot in multiple large studies. Some research suggests that smoking increases the risk of bilateral clubfoot more than unilateral, though this finding is not universal. The mechanism may involve reduced blood flow to the developing limbs or direct toxic effects on muscle and connective tissue development.
Genetic Factors
Certain genetic variants appear to be more strongly associated with bilateral clubfoot. Research published in Human Molecular Genetics has identified variants in the PITX1 gene — which plays a crucial role in limb development — that are particularly associated with bilateral cases.
Treatment of Bilateral Clubfoot
The treatment for bilateral clubfoot is essentially the same as for unilateral: the Ponseti method. Both feet are treated simultaneously.
Casting Phase
During the serial casting phase, both feet are cast at each weekly appointment. The number of casts may differ between the two feet if one is more severe than the other, but typically both feet are corrected at a similar rate. Both legs will be in long-leg plaster casts from toes to above the knee.
Tenotomy
An Achilles tenotomy may be needed for one or both feet. It's common for both heels to need the procedure. When bilateral tenotomies are performed, both are typically done at the same appointment, and the final casts are applied to both legs.
Boots and Bar
The boots-and-bar phase is structurally the same for bilateral clubfoot. Both boots are attached to the bar, with the feet held in abduction and dorsiflexion. The schedule is the same: 23 hours/day for 3 months, then night-time only until age 4-5.
Practical Considerations
While the treatment protocol is the same, having both feet in casts (and later in boots and bar) does present some additional practical challenges:
- Mobility: Babies with bilateral casts are less able to kick and move their legs freely. They adapt, but it's worth providing extra tummy time (supervised) and upper body play opportunities
- Dressing: Going up two sizes in babygrows can help accommodate bilateral casts
- Car seats: Most infant car seats work, but you may need to adjust the buckle between the legs
- Emotional impact: Seeing both feet in casts can be more emotionally challenging for parents. Remember that this phase is temporary and the outcomes are excellent
Outcomes for Bilateral Clubfoot
The outcomes for bilateral clubfoot treated with the Ponseti method are comparable to unilateral clubfoot. Studies consistently show:
- Initial correction rates of 95%+ with the Ponseti method
- Relapse rates of approximately 20-30% (similar to unilateral), mostly related to boots-and-bar compliance
- Long-term function that is excellent — most children walk, run, and participate in all sports without limitation
- Patient satisfaction in adulthood that is high, with most adults reporting good or excellent foot function
Many famous people with clubfoot had bilateral involvement and went on to achieve remarkable things in sport, entertainment, and other fields.
Frequently Asked Questions
Q: Is bilateral clubfoot more serious than unilateral?
A: Not necessarily. Bilateral clubfoot is treated with the same Ponseti method and has similar success rates to unilateral clubfoot. However, bilateral cases are slightly more likely to have an associated underlying condition, which is why the medical team performs a thorough assessment. In terms of treatment outcomes for idiopathic bilateral clubfoot, the prognosis is excellent.
Q: Does bilateral clubfoot mean there's a genetic condition?
A: No. The majority of bilateral clubfoot cases (around 80%) are idiopathic — occurring without any underlying syndrome or genetic condition. While bilateral involvement prompts a more thorough assessment, most babies with bilateral clubfoot are otherwise completely healthy. Associated conditions are the exception, not the rule.
Q: If I had unilateral clubfoot, could my child have bilateral?
A: Yes, this is possible. A parent with clubfoot (whether unilateral or bilateral) has an increased chance of having a child with clubfoot. The child's clubfoot could be unilateral or bilateral, regardless of whether the parent's was one-sided or both-sided. The overall risk for a child when one parent had clubfoot is approximately 3-4%.
Q: Will both feet need the same amount of treatment?
A: Not always. It's common for one foot to be more severely affected than the other. The more affected foot may need additional casts. However, both feet follow the same treatment pathway, and both are typically managed simultaneously.
Q: Can bilateral clubfoot be detected before birth?
A: Yes. Bilateral clubfoot can be detected on the 20-week anomaly ultrasound scan. When bilateral clubfoot is seen on ultrasound, the medical team may recommend additional tests (such as amniocentesis) to check for associated conditions. However, finding bilateral clubfoot on ultrasound does not mean there is definitely an underlying syndrome.
Q: Is bilateral clubfoot hereditary?
A: There is a genetic component to clubfoot, and bilateral cases show a stronger familial association than unilateral cases. However, most babies with bilateral clubfoot have no family history of the condition. If there is a family history, genetic counselling can help you understand the risks for future pregnancies.