Adult Clubfoot Guide

What Muscles Are Weak in Clubfoot?

The most obvious weak area in clubfoot is usually the calf, but the real answer is bigger than “the calf is small.” Clubfoot can affect multiple muscle groups in the lower leg, foot, ankle, and even the way the knee, hip, and back have to compensate.

That matters because parents and adults often ask this question for different reasons. Parents may notice one calf looks smaller than the other and wonder if something went wrong. Adults may feel calf weakness, poor push-off, ankle stiffness, foot fatigue, knee pain, back tightness, or running problems and wonder which muscle is actually failing.

The honest answer is that clubfoot weakness is not one single-muscle problem. The calf muscles are commonly smaller, especially the gastrocnemius and soleus, and imaging finds that difference at every age studied.1 The deep posterior compartment is harder to speak about with the same confidence. The tibialis posterior was described as part of the pull that holds the deformity, but that account dates from 1959 and nobody has returned to it with the imaging available now.3 What has been measured more recently is stiffness: clubfoot tissue tests stiffer than the unaffected side.2 So the compartment is involved. How much of that is weakness and how much is a muscle doing the wrong job is a question the research has not come back to. The tibialis anterior, peroneal muscles, toe muscles, and intrinsic foot muscles may also contribute depending on the person, treatment history, relapse, surgery, and whether the clubfoot is unilateral or bilateral.

This page explains which muscles may be weak, why unilateral and bilateral clubfoot can look different, why weakness can show up as gait compensation, and why strengthening should focus on the whole lower-body system instead of bullying one tiny calf raise machine into solving a lifetime of altered mechanics.

Muscle Groups Commonly Involved in Clubfoot

Short Answer

Clubfoot Can Affect the Calf, Deep Lower-Leg Muscles, Shin Muscles, Peroneals, and Foot Control

The muscles most commonly discussed in clubfoot weakness are the calf muscles, especially the gastrocnemius and soleus. Together, these are part of the triceps surae group and connect into the Achilles tendon. They help with push-off, standing, walking, running, stairs, and absorbing load.

But clubfoot involves more than the visible calf, and this is where the evidence thins. Clubfoot tissue measures stiffer than the unaffected side,2 which is part of why the foot resists correction rather than simply lacking power. The tibialis posterior specifically has been named as part of the deforming pull since 1959,3 and that description has not been retested with modern imaging in the decades since. It is a reasonable account rather than a settled one, and worth knowing it rests on old work. The tibialis anterior, peroneal muscles, toe muscles, and small intrinsic foot muscles may also contribute to weakness, stiffness, poor pressure control, balance issues, or altered gait.

The key is that clubfoot is not always a single weak-muscle problem. It is often a lower-leg development and mechanics problem. In unilateral clubfoot, the affected side may look smaller and weaker compared with the unaffected side. In bilateral clubfoot, both sides may be altered, so weakness can be harder to see but still show up through fatigue, limited motion, poor push-off, pain, or compensation.

Muscle Group 1

The Calf Muscles: Gastrocnemius and Soleus

The calf muscles are usually the most visible difference in clubfoot. In unilateral clubfoot, the affected calf may be noticeably thinner. In bilateral clubfoot, both calves may be smaller or differently developed, so the difference may be less obvious until function is tested.

The calf group matters because it helps move the body forward. It supports push-off, standing endurance, stairs, running, jumping, balance, and deceleration. If the calf is smaller, weaker, or working through limited ankle motion, the body may shift demand somewhere else.

This is why calf weakness can show up far away from the calf. A weak or mechanically limited calf may contribute to knee irritation, hip compensation, back fatigue, opposite-side overload, or the classic adult clubfoot feeling of “I can do the activity, but I pay more for it.”

Read the full calf atrophy guide

Muscle Group 2

The Posterior Compartment: The Deeper Muscles Parents Do Not See

The calf gets attention because you can see it. But the deeper posterior compartment can matter just as much. This area includes muscles such as the tibialis posterior and the long toe flexors. These muscles help support arch position, foot control, inversion, push-off mechanics, and how the foot interacts with the ground.

Research on clubfoot muscle atrophy has pointed strongly toward the posterior compartment. That means the problem is not always only the outer shape of the calf. It may include deeper muscle architecture and control.

This helps explain why someone can do calf raises and still feel mechanically limited. If the deep stabilizing and positioning muscles are underdeveloped, weak, stiff, imbalanced, or altered by surgery, the foot may not load or steer normally even when the visible calf improves.

Muscle Groups 3 and 4

The Front and Side Muscles: Tibialis Anterior, Toe Extensors, and Peroneals

The front and side of the lower leg can also matter in clubfoot. These muscles are not always the most visibly smaller, but they help control foot clearance, ankle position, balance, and side-to-side stability.

The tibialis anterior helps lift the foot upward. The toe extensors assist with lifting the toes and clearing the ground. The peroneal muscles, also called fibularis muscles, help with outward control and side stability. If these muscles are weak, underdeveloped, imbalanced, or poorly coordinated, the person may compensate during walking or running.

This becomes especially important when someone has relapse, foot drop-like patterns, poor clearance, frequent tripping, ankle instability, or a history suggesting nerve involvement. Not every person with clubfoot has nerve dysfunction. But if weakness is severe, changing, or tied to tripping and foot clearance, it deserves evaluation.

Muscle Group 5

The Small Foot Muscles: Pressure, Arch, Toes, and Ground Control

The small muscles inside the foot are easy to ignore because they are not flashy. Nobody posts dramatic gym videos titled “destroying my intrinsic foot muscles today.” But in clubfoot, these small muscles can matter because the foot itself may be smaller, stiffer, differently shaped, or loaded unevenly.

Intrinsic foot muscles help with arch control, toe control, pressure distribution, balance, and ground feel. If the foot is stiff or altered, these muscles may not work through the same range or receive the same feedback as a typical foot.

This does not mean intrinsic exercises fix clubfoot structure. They may help improve awareness and control inside the available structure. That difference matters. You are not asking the small foot muscles to rewrite anatomy. You are asking them to help the system steer better.

Unilateral vs Bilateral

How Muscle Weakness Looks Different in Unilateral and Bilateral Clubfoot

Unilateral and bilateral clubfoot can both involve weakness, calf differences, limited motion, and compensation. But they often look different because the comparison is different.

In unilateral clubfoot, one side is affected and the other side may be closer to typical. That makes differences more visible. Parents may notice one calf is thinner, one foot is smaller, one shoe fits differently, one side tires faster, or the child loads one leg differently.

In bilateral clubfoot, both sides are affected. That can make weakness less obvious because there is no normal opposite side sitting there snitching on the clubfoot side. But bilateral does not mean symmetrical and easy. One side may still be worse. Both calves may be underdeveloped. Both ankles may have limited motion. The person may compensate through hips, knees, back, cadence, stride, or terrain selection.

Embedded Infographic

Unilateral vs Bilateral Muscle Weakness

This no-upload visual helps explain why unilateral weakness is often easier to see, while bilateral weakness may hide inside global function limits.

Compensation Chain

Why Weak Clubfoot Muscles Can Cause Symptoms Beyond the Foot

When clubfoot muscles are weak, underdeveloped, stiff, or poorly coordinated, the body does not simply stop moving. It compensates. That compensation may be useful at first. It is how people keep walking, running, working, and living. But compensation has a cost.

If the calf cannot push off well, the hip may work harder. If the ankle cannot dorsiflex, the knee may change its tracking. If the foot cannot adapt to terrain, the back may absorb more rotation or fatigue. If one side is weaker in unilateral clubfoot, the opposite side may quietly become the unpaid employee of the entire lower body.

This is why the question “what muscles are weak?” should not end with a list. The list matters, but the real issue is how weakness changes the whole system under load.

Training Implications

How Should You Train Weak Muscles in Clubfoot?

Training should match the structure. If the affected foot has flexible residual weakness, the plan may include traditional strengthening, balance, and mobility work. If the person has severe stiffness, surgery history, fusion, arthritis, nerve symptoms, or significant pain, the plan needs more caution.

The goal is not to make every muscle normal. The goal is to build capacity inside the available system. That means strengthening the calf, shin, foot, hip, and core while respecting pain, motion limits, and recovery.

Do not train adult clubfoot like a normal weak ankle unless you enjoy receiving angry memos from your knee and back. Clubfoot muscle weakness is often structural, developmental, and mechanical. That requires a smarter plan than “more calf raises until morale improves.”

Lived Experience

My Personal View: Weakness Is Not Always Where the Pain Shows Up

I was born with bilateral clubfoot. My history includes multiple surgeries, Achilles procedures, tendon work, triple arthrodesis, limited dorsiflexion, altered mechanics, military service, and high-volume endurance running. So when I talk about weak muscles in clubfoot, I am not just thinking about a smaller calf in a mirror.

The calf matters. Push-off matters. Dorsiflexion matters. But the pain and fatigue do not always stay neatly in the foot. For me, symptoms can show up in the knees, low back, outer quad on the worse side, and sometimes sciatic-type patterns after repeated runs. Uneven terrain is harder because the foot and ankle system has less native adaptability. Controlled surfaces are easier because the body can predict the demand.

That is the adult clubfoot lesson: weakness is not always a single muscle failing. Sometimes it is an entire movement strategy working around a structural limit. You can build capacity, and you should. But you have to train the whole system, not just the part that looks smaller.

Related Resources

Build the Bigger Muscle and Mechanics Picture

Muscle weakness in clubfoot connects directly to calf atrophy, exercise selection, limited dorsiflexion, push-off mechanics, gait compensation, pain location, and long-term adult function.