What Causes Bunions on Toes and How to Treat Them

Bunions develop when the joint at the base of the big toe gradually shifts out of alignment, pushing the big toe toward the smaller toes while the head of the first metatarsal bone juts outward. The result is that familiar bony bump on the inner edge of the foot, but the visible lump is really just the surface sign of a deeper structural change in how the bones, tendons, and ligaments of the foot interact. The causes are a tangle of genetics, foot shape, footwear habits, and sometimes underlying conditions, and treatment ranges from simple at-home adjustments to surgery depending on how far the deformity has progressed.

What Actually Happens Inside the Foot

The medical term for a bunion is hallux valgus, and it is classified as a progressive deformity of the first metatarsophalangeal joint, meaning it changes both the anatomy and the biomechanics of the foot over time.¹ Older thinking treated bunions as a simple angular problem visible on a standard X-ray, but newer imaging has revealed that the deformity is three-dimensional. The first metatarsal bone rotates, the arch’s medial column becomes unstable, and the small sesamoid bones under the joint gradually slide out of their normal groove.² Understanding this matters because it explains why bunions tend to get worse without intervention and why a treatment that only addresses the bump itself often falls short.

Genetics and Foot Shape

If your parents or grandparents had bunions, your risk climbs substantially. You do not inherit the bunion itself, but you can inherit the foot architecture that predisposes you to one: a longer first metatarsal, a particular joint shape, or generalized looseness in your ligaments. Research into juvenile hallux valgus suggests at least two distinct pathways: one driven by intrinsic bone characteristics like an angled first metatarsal or an oblique joint surface, and another linked to excessive foot pronation that develops later and worsens more gradually.³ Children and teens who develop bunions often show the first type, which helps explain why some people get bunions despite wearing sensible shoes their entire lives.

Flat feet are one of the most consistent structural risk factors. A systematic review and meta-analysis pooling data from multiple studies found that people with flat feet had about 19% higher odds of developing hallux valgus compared to those with normal arches.⁴ An earlier study of adolescents with bunions put the relationship more starkly, finding that flatfeet occurred at 8 to 24 times the expected rate in that population.⁵ The connection makes mechanical sense: when the arch collapses, it shifts weight and stress onto the inner edge of the foot, gradually nudging the first metatarsal inward.

High Heels and Narrow Shoes

Footwear does not cause bunions in the way most people think. Genes load the gun; shoes can pull the trigger. Tight, narrow toe boxes squeeze the big toe into a valgus position repeatedly, and high heels compound the problem by driving more body weight onto the forefoot. A study using three-dimensional weight-bearing CT scans found that heel height matters in a dose-dependent way. A three-centimeter heel only mildly increased the hallux valgus angle and the intermetatarsal angle, and the changes were not statistically significant. But heels above six centimeters significantly worsened both angles, enough to push the foot from a normal classification into moderate hallux valgus territory.⁶

This partly explains why bunions are more common in women, though biology plays a role too. Women tend to have more ligament laxity than men, particularly around hormonal shifts like pregnancy and menopause, which can make the foot’s stabilizing structures less able to resist the slow drift of the joint. But men get bunions as well, especially those with strong genetic predispositions or flat feet.

Inflammatory Conditions and Other Contributing Factors

Rheumatoid arthritis deserves special mention. The chronic inflammation in this autoimmune condition attacks the synovial lining of joints, and the forefoot is one of its favorite targets. Hallux valgus and deformities of the lesser toes are among the typical presentations.⁷ In these cases the bunion is a downstream consequence of joint destruction, not purely a mechanical problem, which changes the treatment calculus. Gout, psoriatic arthritis, and other inflammatory joint diseases can similarly accelerate or worsen bunion formation in a foot that might otherwise have tolerated its structural quirks for decades.

Occupation and activity level play roles too. Jobs that involve prolonged standing, heavy lifting, or repetitive pushing off the forefoot increase the mechanical load on the first metatarsophalangeal joint. Athletes with hallux valgus show significantly higher forces and pressures through the forefoot and midfoot compared to athletes without bunions, suggesting the deformity shifts how the foot manages load during activity.⁸ This creates a feedback loop: the bunion changes how you walk, and the altered walking pattern places even more stress on the already misaligned joint.

How Bunions Change the Way You Walk

Bunions are not just a cosmetic annoyance. The big toe is supposed to be the last point of contact during each step, providing a powerful push-off. Once the joint shifts, the toe loses leverage, and the body compensates by redistributing pressure to other parts of the foot. Gait analysis research confirms that people with hallux valgus have distinctly different plantar force transfer patterns compared to those without the deformity.⁹ Over time, this can lead to pain under the second and third metatarsal heads, calluses, hammertoes, and even knee or hip issues as the entire lower limb chain adapts to the foot’s altered mechanics.

A related concern after bunion surgery is transfer metatarsalgia, where correcting the big toe’s alignment shifts excess pressure to the neighboring metatarsals. One study found that the length of the second metatarsal relative to the first was a strong predictor: patients whose second metatarsal extended more than about 2 mm beyond the first had significantly higher odds of developing this postoperative pain.¹⁰ Surgeons use this kind of preoperative measurement to plan procedures that minimize this complication.

Conservative Treatment Options

Not every bunion needs surgery. If the deformity is mild to moderate and the pain is manageable, several non-surgical approaches can slow progression and reduce discomfort.

Toe separators and orthoses have the most evidence behind them. A network meta-analysis found that orthoses with a built-in toe separator were the most effective conservative option for correcting the hallux valgus angle, reducing it by roughly 2 to 6 degrees and also improving patients’ sense of well-being.¹¹ Combining toe separators with foot exercises, night splints, and dry needling appears to offer the best overall results for reducing both the hallux valgus angle and the intermetatarsal angle.¹² A separate systematic review confirmed these findings, noting that static orthoses with toe separators and combined exercise-plus-separator regimens consistently performed well across multiple studies.¹³

Foot-strengthening exercises also help, particularly those targeting the intrinsic muscles of the foot. Weak muscles around the first metatarsophalangeal joint may contribute to bunion-related pain and reduced mobility, and research suggests that targeted strengthening can improve both.¹⁴ Exercises like short-foot contractions (where you try to shorten the arch by pulling the ball of the foot toward the heel without curling the toes), towel scrunches, and deliberate big-toe abduction drills are commonly recommended. The goal is to rebuild the muscular support that helps keep the first metatarsal from drifting.

Footwear changes are the simplest intervention. Switching to shoes with a wide toe box, a low heel, and adequate arch support removes the external forces that accelerate the deformity. This will not reverse a bunion, but it can meaningfully slow progression and reduce daily pain. Some people benefit from custom orthotics that redistribute pressure away from the bunion and support the medial arch.

When Surgery Becomes the Right Call

Surgery typically enters the conversation when conservative measures have not controlled the pain, when the deformity is severe enough to interfere with daily activities, or when the big toe has started crowding and damaging the lesser toes. There are well over a hundred described surgical techniques for hallux valgus, but the main categories boil down to osteotomies (cutting and repositioning the bone), joint fusions, and soft tissue procedures, often used in combination.

Minimally invasive bunion surgery has gained significant ground in recent years. A multi-dimensional systematic review found that minimally invasive approaches offered faster recovery, higher patient satisfaction, fewer wound complications, and shorter operating times compared to traditional open surgery.¹⁵ Radiographic correction of the angles was durable, and the procedures were more cost-effective over time. However, for severe deformities, open techniques remained more reliable because complex corrections are harder to achieve through small incisions.

When comparing specific techniques, studies have found similar radiographic outcomes between minimally invasive approaches and the modified Lapidus procedure (a fusion of the first tarsometatarsal joint). Minimally invasive surgery was significantly faster to perform, and bunion recurrence rates were low in both groups.¹⁶ In older patients, both minimally invasive and open surgery achieved comparable correction at one and two years, with both groups showing meaningful improvements in pain and physical function by the two-year mark.¹⁷

Complication rates with newer minimally invasive techniques are generally acceptable. A retrospective review of fourth-generation minimally invasive bunion surgery found that about 89% of procedures had no notable postoperative complications. The most common issues were hardware failure (about 8%), reoperation (about 7%), and wound problems (about 7%). Serious complications like fracture, joint stiffness, or recurrence each occurred in fewer than 3% of cases.¹⁸

The Recurrence Problem

One of the most frustrating realities of bunion surgery is that the deformity can come back. A systematic review and meta-analysis found a pooled recurrence rate of roughly 25%.¹⁹ That number varies widely depending on the initial severity, the surgical technique, and how well the correction holds. The strongest predictors of recurrence are the preoperative severity of the deformity and the adequacy of the correction achieved during surgery. A larger hallux valgus angle going in and a less-than-ideal correction coming out both raise the odds of the bunion returning.

Postoperative management plays a real role in whether a surgical correction lasts. Structured rehabilitation, appropriate footwear after surgery, and physiotherapy all help maintain the correction.²⁰ The type of fixation used during surgery also matters: one study found that temporary wire fixation carried significantly higher odds of recurrence compared to more rigid fixation methods.²¹ Choosing an experienced surgeon who matches the procedure to the specific anatomy and severity of the bunion appears to be the single most important factor in getting a durable result.

Modern Imaging and Why It Matters for Treatment Decisions

Traditionally, bunions have been diagnosed and measured with standard weight-bearing X-rays taken from the front and side. These two-dimensional images capture the hallux valgus angle and the intermetatarsal angle, the two numbers used to classify severity as mild, moderate, or severe. But as the understanding of bunions as a three-dimensional deformity has grown, weight-bearing CT scans have become increasingly valuable. These scans reveal the rotational component of the deformity, including how much the first metatarsal has pronated, that standard X-rays simply miss.²²

The practical upshot for patients is that a surgeon using weight-bearing CT can plan a more precise correction, addressing not just the side-to-side angulation but also the rotation and instability that drive recurrence. Measurements taken from these scans show very good reliability between different observers, meaning the numbers are consistent regardless of who reads the scan.²³ While not every bunion requires this level of imaging, it is becoming the standard of care for surgical planning, particularly for moderate-to-severe cases or revision surgeries where getting the correction right the first time is critical.

Bunions in Children and Teenagers

Juvenile hallux valgus is less common but can be more challenging to manage than the adult version. Kids’ bones are still growing, which means the deformity can worsen rapidly during growth spurts, but it also opens up treatment options that are not available to adults. One approach combines a growth-plate procedure on the first metatarsal (hemiepiphysiodesis, which gently redirects growth) with a calcaneal-stop screw to correct an accompanying flatfoot.³ This works with the child’s growth rather than against it, and when the bunion co-exists with flat feet, treating both together addresses the underlying mechanical problem rather than just the visible bump.

Parents who notice a bunion developing in their child’s foot should not assume it will resolve on its own. The “wait and see” approach can work for very mild cases, especially with supportive footwear and activity modification, but a consultation with a pediatric orthopedic specialist is worth pursuing if the angle is visibly worsening or causing pain. Early intervention in children often yields better long-term results than waiting until the deformity becomes severe.

How Bunions Affect Quality of Life

The impact of bunions goes well beyond the foot. People with moderate to severe bunions often limit their physical activity to avoid pain, struggle to find shoes that fit, and feel self-conscious about the appearance of their feet. Studies on bunionettes (a similar deformity on the outside of the foot, sometimes called a tailor’s bunion) have found that more severe grades of the deformity are associated with lower scores in foot pain, foot function, footwear comfort, and general foot health. Men with the most severe grade actually reported greater limitation than women with the same severity. The psychological toll of chronic foot pain and restricted shoe choices is easy to underestimate, and it is worth factoring into treatment decisions rather than waiting until the bunion becomes disabling.

Bunions also have a documented effect on balance and fall risk in older adults. When the big toe cannot grip the ground properly during walking, the body’s ability to make quick postural corrections diminishes. For an otherwise healthy 35-year-old, this is a minor inconvenience. For a 75-year-old with reduced muscle mass and reaction time, it becomes a genuine safety concern. This is one reason many foot and ankle specialists encourage older patients to consider surgical correction when conservative measures are no longer keeping up, even though recovery from foot surgery can be slow in this age group.