Bunions on the feet: why they appear

A "bunion" is a common term for a hallux valgus, a deformity of the big toe in which the toe deviates outward, forming a painful medial bulge at the base. The deformity develops gradually over years and affects not only the bones but also the ligaments, tendons, and sesamoid bones, so it's more accurately considered a multifactorial, three-dimensional biomechanical disorder. [1]

Prevalence is high and increases with age: systematic reviews show a prevalence of approximately 23% in adults and over 30% in the elderly, with a predominance in women. These figures explain why the topic of "why bunions occur" is important not only for aesthetics but also for quality of life, pain when walking, and choosing comfortable shoes. [2]

The modern view is that there is no single "main cause." Typically, a puzzle is formed by predisposition, the shape and mobility of the first ray, footwear and load characteristics, the overall condition of the connective tissue, and associated diseases. The contribution of these factors varies from person to person, but the result is the same: deterioration of the coordinated function of the first metatarsophalangeal joint. [3]

Understanding the causes is important because many of them are modifiable. Proper toe width, moderate heel height, weight control, timely replacement of worn-out shoes, and arch support reduce stress on the medial edge and slow progression, especially in the early stages. [4]

How Deformation Forms: Three-Plane Biomechanics

In hallux valgus, the big toe deviates outward, and the first metatarsal bone moves medially and often rotates around its axis. This is a triplanar deformity: displacement occurs in the frontal, sagittal, and horizontal planes, and the sesamoid bones shift laterally and lose their normal "locking" effect. [5]

Most clinical and tomographic studies confirm the role of first metatarsal rotation: up to 80-90% of patients have pronation, which alters the joint contact surfaces and displaces the sesamoid bones. This explains why simply "bringing the angles together" without considering rotation can lead to undercorrection and recurrence of symptoms. [6]

Hypermobility or instability of the first ray increases displacement. With increased mobility of the medial column of the foot, the load during rolling is transferred to the soft tissues at the head of the first metatarsal bone, which creates a vicious cycle: pain, swelling, further displacement, and friction in shoes. [7]

Weight-bearing computed tomography (CT) scans provided further insight: the deformity affects not only the toe and first metatarsal, but also the alignment of the sesamoid bones and the hindfoot. In some patients, connections were found between the alignment of the hindfoot and the rotation of the first ray, highlighting the systemic nature of the problem. [8]

Table 1. Three key elements of deformation

Element	What's happening	Why is this important?
Deviation of the first finger	The finger goes outward	Friction and pain in shoes
Displacement of the first metatarsal bone	Medial drift and elevation	Redistribution of pressure on the medial edge
Rotation and sesamoid bones	Pronation and lateralization	Loss of "locking", joint instability
Summarized from clinical reviews and imaging studies.[9]

External factors: footwear and load

A narrow toe box, high heel, and short shoes increase pressure on the medial forefoot, pushing the big toe toward the adjacent toe and increasing friction in the bunion area. This isn't always the primary cause, but it often accelerates the deformity, especially if there's a pre-existing predisposition. [10]

Studies of in-shoe pressure show that widening the toe box and proper sizing reduce peak pressures on the metatarsophalangeal joint and subjective pain. This is a simple, accessible, and evidence-based approach to early prevention. [11]

It's important to avoid wearing shoes that are too short for children and adolescents. Observational studies demonstrate an increased risk of lateral deviation of the big toe with street and indoor shoes that are 1-3 sizes shorter than the optimal size, with the risk increasing as the pair gets shorter. [12]

Even in adults, prolonged standing, working on hard surfaces, and excessive impact loads can exacerbate the problem if shoes are narrow or stiff at the front. Alternating pairs, shock-absorbing insoles, and work mats can reduce peak loads and irritation in the medial edge area. [13]

Table 2. Shoe provocateurs and quick solutions

Provocateur	What are we changing today?
Narrow toe area	Transition to models with a wide front
High heel	Reducing heel height in everyday life
Short pair	Length allowance 10-12 mm
Hard floors and long shifts	Shock-absorbing mat, shoe rotation
Summary of clinical sources and pressure studies. [14]

Internal factors: predisposition, connective tissue, diseases

Hereditary predisposition is supported by family and twin studies: in some individuals, genetic factors play a significant role, while in others, environmental factors, particularly footwear habits, dominate. Modern genetic studies indicate moderate to high heritability and the possible involvement of copy number variants in shaping the phenotype. [15]

The condition of the connective tissue is also important. Generalized ligamentous laxity and hypermobility of the first ray increase the risk, as the medial column of the foot is less able to resist the deforming forces with each step. This factor is often associated with a flat-valgus foot position. [16]

Inflammatory diseases, primarily rheumatoid arthritis, accelerate the remodeling of the articular surfaces and soft tissues of the forefoot, increasing the likelihood of deformity and its progression. In such patients, treatment requires earlier shoe and arch correction to reduce friction and pain. [17]

Excess body weight increases the overall load on the forefoot, and in some patients, flat feet and changes in the hindfoot are associated with greater severity of the deformity. These factors do not "cause" bunions alone, but they significantly increase their symptoms and pain. [18]

Table 3. Internal risk factors and their contribution

Factor	Mechanism	What can be done
Heritability	Shape and mobility of the first ray	Early prevention, wider toe box
Hypermobility of the first ray	Medial column instability	Arch support, shoe control
Inflammatory arthritis	Joint and soft tissue remodeling	Early control of inflammation, shoe measures
Flat feet, excess body weight	Increased medial loads	Weight loss, insoles, shoes
Summarized from genetic and clinical sources. [19]

Children and Adolescents: What the Evidence Teaches

Large-scale pediatric studies have shown a simple correlation: the shorter the shoe relative to the foot, the higher the risk of increased big toe angle. Shoes that are 2-3 sizes shorter than the optimum are particularly unfavorable. This argument supports regularly checking the length and width of children's shoes. [20]

Changing to shoes with sufficient length and width reduces mechanical pressure on the medial edge and allows the soft tissues to "keep pace" with the foot's growth. As a result, the likelihood of pain and blisters decreases in the coming months, and the risk of developing permanent deformities is reduced. [21]

Early complaints in adolescents often reflect a combination of footwear factors and increased activity. At this stage, shoe correction, moderate impact load limitation, and exercises targeting the "core of the foot"—the short muscles responsible for arch support and big toe abduction—are effective. [22]

If pain and “collision” of the first and second toes persist despite wearing correct footwear, an in-person assessment is necessary to rule out other causes and choose further tactics, primarily non-surgical means of protection against friction. [23]

Table 4. Childhood prevention in three rules

Rule	How to check
Length allowance 10-12 mm	The toes move freely, the toe does not press
Sufficient width	The toe area does not squeeze the toes
Regular check	Every 2-3 months during active growth
Summary of pediatric shoe fit studies. [24]

What does epidemiology say: who is at risk?

Meta-analyses report an overall prevalence of approximately 20-30% in adults and over 30% in the elderly, with the deformity occurring more frequently in women than in men. This reflects differences in anatomy, footwear habits, and connective tissue status. [25]

Prospective observations in people over 50 years of age show a significant rate of "new" cases over the years, especially in those who already had foot pain, poor physical health, and poor footwear habits in the past. This emphasizes the importance of primary prevention. [26]

In old age, deformity is associated not only with pain but also with the risk of falls and activity limitations. Footwear control and pain reduction are just as important as the "beauty" of the foot, as they help maintain independence and safety. [27]

In inflammatory arthritis and severe hypermobility of the first ray, the risk of progression is higher: in these groups, earlier and more aggressive correction of load and friction factors is required, and if ineffective, surgical approaches should be discussed. [28]

Table 5. Epidemiological emphases

Group	What is typical
Women	Higher prevalence
Elderly	Increase in frequency and severity
People with foot pain	Higher risk of occurrence and progression
Inflammatory arthritis	Fast progress, more restrictions
Summarized from meta-analyses and prospective data. [29]

Common myths about the causes and what is actually

Myth: "It's all about tight shoes." In reality, shoes often accelerate an existing predisposition, rather than being the primary cause. People with genetic and biomechanical vulnerabilities react more quickly and severely to a narrow toe box. [30]

Myth: "If there's no heel, bunions won't form." Even without a heel, a narrow or short toe box increases medial loads. Both requirements are correct: sufficient width and the correct length. [31]

Myth: "It's purely hereditary; shoes have nothing to do with it." Research shows the variable role of genetics and the measurable contribution of shoe habits, especially in children and women. The balance of factors varies from person to person. [32]

Myth: "Once it starts, it inevitably ends with surgery." In the early stages, proper footwear, friction protection, and arch support significantly reduce pain and slow progression, while surgery is considered only when pain and limitations persist. [33]

Table 6. Myths and facts about the causes of "bunion"

Myth	Fact
Only shoes "make a bone"	This is a multifactorial problem.
Without heels the risk disappears	A narrow toe and short length are still dangerous
Heredity decides everything	Genetics, environment, and stress are all important.
The onset of deformation always leads to surgery	Early intervention reduces pain and slows progression
Summary of reviews and clinical guidelines. [34]

How to reduce the impact of causes today

Check the length and width of the shoe: there's 10-12 mm of room at the front, the toes move freely, and the toe area doesn't press on the medial edge. This will reduce peak pressure and friction in the deformation zone. [35]

Minimize heel height on weekdays and alternate pairs, especially if you stand a lot. Use shock-absorbing insoles and mats at your workstation if necessary. [36]

Support the arch and train the “core of the foot”: Abduction of the big toe and the “dome of the foot” improve medial column control and load distribution during walking. [37]

Monitor early signs of progress: increasing pain at the “bump,” calluses between the first and second toes, difficulty finding shoes – these are reasons for an in-person assessment and adjustment of tactics. [38]