One calf smaller than the other

If the difference has been there as long as you can remember, it is almost certainly structural and permanent, and the strength difference is not. If it turned up later, or is still changing, that is a different question with a different answer, and it is worth having looked at. Both are below.

Written by Heath, who has lived it: casts from birth, a fusion at sixteen, the US Army, and distance running.

Test it rather than guess

Four things you can check yourself, right now. The point is not the numbers. It is separating what is fixed from what is simply untrained.

Single-leg heel raises

Fingertips on a wall for balance only. Rise as high as you can on the affected leg, lower slowly, repeat until you cannot reach full height. Count them.

How many?

That is a functional calf, whatever it looks like from behind.

Common, and the most improvable range there is.

A big functional deficit. Start with two-legged raises and build.

Worth establishing why before training. Strength, ankle range and pain are three different reasons.

Compare the two sides

Do the same test on the unaffected side. If both feet were affected, use whichever side feels stronger as the reference.

The affected side manages

A small gap here means the muscle is being used well.

A typical untrained gap instead of a structural limit.

Larger than atrophy alone usually explains.

How high does the heel actually go?

Watch in a mirror or have someone look. Compare the height your heel reaches on each side at the top of a raise.

On the affected side

Full range with load is a good sign about the whole chain.

Could be strength or could be the joint. Test 4 separates them.

Suggests the limit is at the joint or in the tendon, not in the muscle belly.

Does anything hurt while you do it?

Muscle burn does not count. Sharp, deep or joint-line pain does.

During the raises

Then training is straightforwardly available to you.

Manageable, but reduce range instead of pushing through it.

Pain at the joint is a reason to have it assessed, not a reason to train harder.

What your answers suggest Four tests, about five minutes

You need a wall for balance and somewhere to stand. Do the tests on the clubfoot (club foot) side and then the other side, and answer for the affected one.

First question

Has it always been there, or did it appear?

That one answer splits the whole subject. A calf that has been smaller for as long as you can remember is a structural difference you were born with, and the rest of this page is about living with it. A calf that has become smaller, or is still shrinking, is a different problem and belongs with a clinician rather than a website.

A published case series of one-sided calf wasting lists the usual causes: a nerve root irritated in the lower back, a tibial nerve squeezed at the back of the knee by a Baker’s cyst, an uneven muscle disease, and plain disuse.4 The authors make the point that looking at the leg does not settle it. Nerve conduction studies and ultrasound do.4

There since childhoodClubfoot, or another difference present from birth. The muscle is smaller from the start, and no amount of training makes the two sides match.

After time off the legWeeks in a cast, a boot or on crutches shrink a calf quickly. This one comes back, though more slowly than it went.

After an Achilles ruptureIt can stay. Fourteen years after repair, MRI found the soleus and gastrocnemius 11 to 13 percent smaller than the other leg, with 12 to 18 percent less push-off strength.5

A nerve problemBack-related nerve root trouble, or pressure on the tibial nerve behind the knee. Often with numbness, tingling or weakness rather than just a size difference.4

Worth being seen for: a calf that is visibly shrinking now, new weakness pushing off or standing on tiptoe, numbness or pins and needles, back pain alongside it, or pain in the thinner leg. None of those are explained by having been born with a smaller calf.

If you were born with it

Why the clubfoot calf is smaller

It is part of the condition, not a consequence of the treatment. The calf on a clubfoot side is already smaller before a single cast goes on1. It has been shown in infants and even before bir1th. The muscle contains fewer fibers, smaller fibers, and proportionally more fibrous tissue than the other side.

This matters because a great many adults quietly believe their calf shrank because of something that was done to them, or because they did not try hard enough as a teenager. Neither is true, and both are worth putting down.

The size was decided before you were born. The strength was not.

What follows from that is a genuinely useful split. Circumference is largely fixed. Children with one-sided clubfoot, measured at five, seven and ten years old, averaged about two centimeters less calf girth on the treated side, and the gap was there at every age; with both feet involved the two sides differed by under half a centimeter.6 A year of training does not remove it. Three-dimensional ultrasound in children aged two to twelve who were doing well after Ponseti treatment found the same thing from the other direction: smaller calf muscle volume and a larger Achilles tendon volume on the affected side, with the size of the gap unrelated to age.2 Force production is not fixed. A smaller muscle has a lower ceiling, and most people sit nowhere near their own ceiling.

What actually changes what

If you train it	Realistic change	Timescale
Calf circumference	Very little, often none	Not applicable
Heel raise repetitions	Frequently doubles or better	8 to 12 weeks
Walking endurance	Noticeably improved	6 to 10 weeks
Push-off power	Improved, rarely equalized	3 to 6 months
End-of-day aching	Often reduced	4 to 8 weeks
Ankle joint range	Unchanged by strength work	Not applicable

Two rows say no. Both are the structural ones, and no amount of effort moves them. Every other row is available, which is a much better ratio than most people assume when they first look at their own leg in a mirror.

Practically: slow single-leg raises through whatever range the ankle allows, taken to genuine fatigue, three times a week. Add the bent-knee version, which targets the soleus underneath. That is the muscle doing most of the work when you walk, and it is the one most often left out. If a limp appears when you are tired, this is usually the lever that matters.

Video · 7:05Strength work adapted for an ankle that barely moves. Watch on YouTube →

The part nobody puts in the clinical literature

The calf is the thing adults with clubfoot mention most about appearance. Not the foot. The calf. It is the part that shows in shorts, that shows in photographs, and that gets asked about by people who have not noticed anything else.

I spent my teens and most of my twenties avoiding shorts over it, and I ran a good deal further than most people on the leg I was hiding. Both of those things were true at the same time. It is worth saying plainly that the discomfort is common and that it is not proportionate to what the leg can do.

Heath mid-stride on grass in a vest, cap and sunglasses, both feet in frame — **Now · the author**Both calves in frame, in shorts. Both of mine are small, which is the tell of every clubfooter, and it has not stopped me running distance.

Sources

Where this comes from

1 Leg muscle atrophy in idiopathic congenital clubfoot: is it primitive or acquired?Journal of Children’s Orthopaedics, 2009 2 Muscle-tendon properties assessed by three-dimensional ultrasound in clubfootJournal of Children’s Orthopaedics, 2025 3 Diagnosis and Treatment of Idiopathic Congenital ClubfootAmerican Academy of Pediatrics, 2022 4 Shields LB, Iyer VG, Zhang YP, Shields CB. Unilateral Calf Atrophy: A Case Series of Clinical and Electrodiagnostic Findings With a Review of the LiteratureCureus, 2024 5 Heikkinen J, et al. Tendon Length, Calf Muscle Atrophy, and Strength Deficit After Acute Achilles Tendon Rupture: Long-Term Follow-upJournal of Bone and Joint Surgery, 2017 6 Baird GO, et al. Symmetry of Shoe Size and Calf Girth in Children With Treated Idiopathic Clubfoot: A Longitudinal StudyJournal of Pediatric Orthopaedics, 2022

The smaller calf

Why is one calf smaller than the other?

If it has been that way since childhood it is usually structural: in clubfoot the calf is smaller from birth, as part of the condition rather than a result of treatment. If it developed later, the common causes are disuse after time in a cast or on crutches, an Achilles rupture, or a nerve problem such as an irritated nerve root in the lower back.

One calf is getting smaller. Should I see a doctor?

Yes. A calf that is actively shrinking, or comes with new weakness, numbness, tingling or back pain, is not explained by a difference you were born with. Nerve conduction studies and ultrasound are what sort out the cause; looking at the leg does not.

Can you fix a calf that is smaller than the other?

You can change the strength but rarely the size. Where the difference is structural, the two sides do not end up matching however much you train. Where it followed disuse, size does return, more slowly than it was lost.

Is it normal to have one calf bigger than the other?

Small side-to-side differences are common and mean nothing on their own. What matters is whether the difference is stable, and whether anything comes with it: weakness, numbness, pain, or a change you can date.

Could one calf being smaller be a sign of something serious?

It is one item on a long list, and the list is longer than the fear that usually brings people to it. The published differential for one-sided calf wasting runs from an irritated nerve root in the lower back, which is the most common of them, through uneven muscle disease, tibial nerve compression behind the knee, amyotrophic lateral sclerosis, and plain disuse.4 The point the authors make is that the list cannot be narrowed by looking at the leg. Nerve conduction studies and ultrasound are what separate these.4 A calf that has been smaller since childhood and has not changed is a different situation from one that is wasting now. If yours is changing, or the leg is getting weaker, ask for the testing rather than for an opinion about the shape.

Why is my left leg thinner than my right?

The side itself tells you very little. What matters is when it started and whether it is stable. A difference that has been there as long as you can remember usually belongs to how the leg was built, and in one-sided clubfoot the smaller calf is on the affected side and has been since birth. A difference that appeared in an adult leg belongs to whatever happened to that leg, or to the nerves supplying it, and that is worth having examined.

Why is the calf smaller on the clubfoot side?

The calf muscle is smaller from birth as part of the condition itself, not as a result of treatment. It contains fewer and smaller muscle fibers and more fibrous tissue, and this is present before any casting or surgery happens.

Can the calf be made the same size as the other one?

Almost never. The size difference is structural and persists whatever you do. Strength is a separate matter and can improve substantially without the calf changing much in appearance.

Does a smaller calf mean a weaker calf?

It means a lower ceiling, not a fixed level. Many adults with a visibly smaller calf are far weaker than they need to be simply because it has never been trained, and that gap is worth closing.

How much size difference is typical?

Measured in children at five, seven and ten years old, one-sided clubfoot averaged about two centimeters less calf girth on the treated side at every age. With both feet involved the two sides differed by under half a centimeter, because both calves are affected. The same study found the involved foot needed a shoe about one and a half sizes smaller.

What is the best exercise for it?

Single-leg heel raises, done slowly, through as much range as the ankle allows, to genuine fatigue. Bent-knee versions target the soleus underneath and matter as much as the straight-leg version for walking endurance.

Does calf atrophy get worse with age?

The underlying difference does not, but general age-related muscle loss lands on a smaller starting muscle, so the functional effect is felt earlier and more sharply than on the other side.

Will building the calf reduce my pain?

Often it helps, because a stronger calf absorbs load that would otherwise pass into the midfoot, knee and hip. It does not address joint pain coming from arthritis, which is a separate problem.

Should I be self-conscious about it?

Many people are, particularly in their teens and twenties. It is the single most commonly mentioned appearance concern in adult clubfoot, and worth naming instead of pretending away, though it says nothing about capability.

The smaller foot →The same question, one level down the leg. Limping →Weak push-off is one of the four causes, and the trainable one. Why it worsens →How losing strength turns into losing comfort. Found on the 20-week scan →What a prenatal diagnosis does and does not tell you.