Clubfoot Foot Size Difference: Why It Happens and What to Do
A clubfoot foot size difference is one of the most common long-term features of treated congenital talipes equinovarus. If your child has unilateral (one-sided) clubfoot, you will almost certainly notice that the affected foot is slightly smaller than the other. This guide explains why the size difference occurs, how much difference is typical, whether it affects function, and practical strategies for managing shoes and footwear in the UK.
Why Is the Clubfoot Foot Smaller?
The size difference is not caused by the treatment — it is an inherent feature of the condition itself. Several factors contribute:
Abnormal Bone Development
In clubfoot, the talus (the main ankle bone) is abnormally shaped from birth — it is smaller, flatter, and more wedge-shaped than normal. The navicular bone is displaced medially, and the calcaneus (heel bone) is smaller and tilted. These structural differences are present before any treatment begins and persist even after successful correction with the Ponseti method.
Reduced Blood Supply
Research has shown that the arterial blood supply to the clubfoot is often abnormal, with a higher rate of absent or hypoplastic (underdeveloped) anterior tibial artery. Reduced blood flow during fetal development may contribute to smaller bone and soft-tissue growth on the affected side.
Muscle Underdevelopment
The calf muscles and intrinsic foot muscles on the affected side are typically smaller. Reduced muscle bulk means less soft tissue surrounding the bones, contributing to a smaller overall foot circumference and volume.
Cartilage and Growth Plate Effects
The growth plates in the bones of the clubfoot may produce slightly less bone over time than those on the unaffected side. This progressive, small difference in growth rate means the size gap may widen slightly during childhood, stabilising by skeletal maturity (around age 14–16 for the foot).
How Much Difference Is Typical?
Published research gives us good data on expected size differences:
- Foot length: The affected foot is typically 0.5–1.5 cm shorter than the unaffected foot. A study by Chesney et al. (2008) in the Journal of Bone and Joint Surgery found an average length difference of 0.9 cm in Ponseti-treated feet at 10-year follow-up.
- Foot width: The affected foot tends to be 3–5 mm narrower.
- Shoe size: This translates to approximately 0.5–1.5 UK shoe sizes difference. Some children need shoes in two different sizes.
- Foot circumference: The overall volume of the affected foot is smaller, meaning the shoe may feel looser even when the length is correct.
In bilateral (both feet) clubfoot, the size difference between the two feet is usually minimal — both feet are affected similarly. However, both feet may be slightly smaller than average for the child's age and height.
Does the Size Difference Affect Function?
In the vast majority of cases, no. The foot size difference is a cosmetic finding that does not impair walking, running, sport, or any other physical activity. Children with a 1-cm difference in foot length adapt completely without conscious effort.
However, poorly fitting shoes on the smaller foot can cause problems:
- Blisters and rubbing: A shoe that is too large slides during walking, causing friction.
- Tripping: An oversized shoe on the affected side can catch on the ground.
- Compensatory gait changes: To keep a loose shoe on, children may subconsciously grip with their toes or alter their walking pattern.
Getting the shoe fit right on both feet prevents these issues entirely.
Practical Shoe Solutions in the UK
Buying Two Different Sizes
Several UK options exist for purchasing shoes in mismatched sizes:
- Clarks: Some Clarks stores will sell odd-sized pairs. Ask the manager — the policy varies by store, and it may require ordering in.
- Start-rite: Their online store occasionally offers split-size purchasing. Contact customer service directly to ask.
- Odd Shoe Swap (Facebook group): A UK-based community where parents swap single shoes. If you buy size 9 and need a size 8 for the other foot, another family in the opposite situation will trade with you.
- National Odd Shoe Exchange: A charity that facilitates odd-sized shoe exchanges.
- Buying two pairs: The simplest (if most expensive) approach. Buy one pair in each size and donate or swap the spares. For school shoes bought once or twice a year, the cost may be manageable.
Insoles and Padding
If the size difference is small (half a size or less), insoles can compensate:
- A thin foam insole in the smaller foot's shoe takes up extra volume.
- Heel grips stuck inside the shoe back prevent the heel slipping.
- A slightly thicker sock on the smaller foot fills the space.
Custom Shoes and Orthotics
If the size difference is significant (more than 1.5 sizes) or if there are additional alignment issues, your orthopaedic team may refer you to an orthotist for custom footwear. NHS provision varies by region — ask your consultant about what is available locally.
Size Difference Over Time
The foot size difference tends to follow this pattern:
- Birth to 2 years: Difference is small and often not noticeable — baby shoes are soft and accommodate some variation.
- 2–5 years: The difference becomes more apparent as the child moves into structured shoes. This is when parents typically first notice they need different sizes.
- 5–12 years: The difference remains stable or increases slightly. Regular shoe fitting is important during this period of rapid foot growth.
- 12–16 years: The growth plates close and the size difference becomes permanent. Typical final difference: 0.5–1.5 cm in length.
- Adulthood: The size difference persists but rarely causes functional problems. Most adults with treated clubfoot manage the difference easily with standard shoe strategies.
Emotional Impact
For some children and teenagers, the visible size difference becomes a source of self-consciousness, especially during the peer-comparison years of secondary school. Strategies that help:
- Open, age-appropriate conversations about why the feet are different
- Pointing to famous people with clubfoot who have thrived
- Ensuring shoes look identical (same style, same colour, just different sizes)
- Connecting with other young people through clubfoot support communities
- If self-consciousness becomes significant, consider referral for counselling — see our emotional support guide
When to Raise Concerns
A stable, small size difference is normal and expected. However, contact your orthopaedic team if:
- The size difference is increasing rapidly (more than 5 mm per year)
- The smaller foot is becoming stiff or losing range of motion
- The foot is causing pain
- The foot appears to be turning inward again — this could indicate relapse
- Shoe fitting is becoming impossible despite the strategies above
Frequently Asked Questions
Q: Will the foot size difference get worse over time?
A: The difference typically increases slightly during childhood growth (as the unaffected foot grows faster) and then stabilises at skeletal maturity. It does not keep getting worse indefinitely. Most adults report a stable 0.5–1.5 cm difference.
Q: Can physiotherapy or exercises make the foot grow bigger?
A: No. The size difference is determined by the underlying bone structure and blood supply, which cannot be changed by exercise. Physiotherapy improves flexibility, strength, and function — but it does not affect foot length.
Q: Does the foot size difference indicate incomplete correction?
A: No. A size difference is a normal feature of treated clubfoot, even when correction is complete and the foot is fully functional. Your orthopaedic team assesses correction based on alignment, range of motion, and Pirani score — not foot size.
Q: Can I get shoes on the NHS for my child's different-sized feet?
A: NHS provision varies. If the size difference is significant enough to require custom or surgical footwear, this may be available through your orthopaedic or orthotics department. For standard shoes in different sizes, the NHS does not typically cover the cost, but your team can advise on local resources and charities that help.
Q: Will my child need shoe lifts?
A: Shoe lifts (heel raises) address leg length differences, not foot size differences. If the affected leg is also shorter (uncommon in isolated clubfoot), a heel raise inside the shoe may be recommended. For a simple foot size difference without leg length discrepancy, lifts are not needed — just properly fitted shoes.