Metatarsus adductus (MA) is one of the most frequently encountered congenital foot deformities in paediatric medicine, characterised by an inward curvature of the forefoot relative to the hindfoot. Sometimes described colloquially as “in-toeing,” the condition affects the metatarsal bones — the five long bones of the midfoot — which deviate medially, giving the foot a distinctly curved or kidney-bean shape when viewed from below. Though often alarming to new parents who notice the unusual appearance of their infant’s feet, metatarsus adductus is in the vast majority of cases a benign and self-resolving condition. Nevertheless, a clear understanding of its aetiology, diagnosis, and management remains essential for clinicians, parents, and allied health professionals alike.
Aetiology and Epidemiology
Metatarsus adductus occurs in approximately one to two per thousand live births, making it among the most common musculoskeletal anomalies seen in neonates. Its cause is generally attributed to intrauterine positional factors — specifically, the position of the foetus within the uterus during the final weeks of pregnancy. When the foot is persistently compressed or held in an adducted position against the uterine wall or the other limb, the soft tissues and developing bones may adapt accordingly. This theory is supported by the higher prevalence of MA in firstborn children (where the uterus is typically less distensible), in multiple pregnancies, and in cases of oligohydramnios, all of which reduce available intrauterine space.
There is also evidence of a genetic predisposition. Studies have reported familial clustering, with a higher incidence among siblings and first-degree relatives of affected individuals. Additionally, metatarsus adductus is more commonly observed in females than males, though the reason for this sex-based difference is not fully understood. The condition is bilateral in approximately 50% of cases, further suggesting a systemic developmental influence rather than purely mechanical compression.
Clinical Presentation and Classification
The hallmark of metatarsus adductus is a forefoot that curves inward while the hindfoot and ankle appear normal or near-normal. On clinical examination, the lateral border of the foot — which should be straight — is visibly convex, and a deep crease may be present along the medial arch. The heel is typically in a neutral or slightly valgus position, which distinguishes MA from clubfoot (talipes equinovarus), a more severe and structurally complex deformity that also involves the hindfoot and ankle.
Clinicians commonly use the Bleck classification system to grade the severity of MA based on the flexibility of the foot. In mild cases, the foot can be passively corrected beyond the neutral position with gentle pressure — these cases almost universally resolve without intervention. In moderate cases, the foot corrects only to a neutral position with manipulation. Severe cases are those in which the foot cannot be passively corrected to neutral, and these are the cases most likely to require active treatment. A simple assessment tool is the heel bisector line: a line drawn through the midpoint of the heel should normally pass through the second or third toe; in MA, this line falls lateral to the normal range, pointing toward the fourth or fifth toe depending on severity.
Natural History
The natural history of metatarsus adductus is largely favourable. Studies have demonstrated that the majority of cases — estimates range from 85 to 90 percent — resolve spontaneously without any formal intervention by the time the child reaches two to four years of age. The flexibility of the foot at the time of diagnosis is the strongest predictor of spontaneous resolution: flexible deformities almost always self-correct as the child begins to walk and weight-bear, which itself provides a corrective stimulus to the developing foot architecture.
This benign natural course must, however, be balanced against the recognition that a subset of children — particularly those with rigid or severe deformity — will not resolve without treatment. If left untreated, persistent metatarsus adductus can lead to difficulties fitting standard footwear, an abnormal gait pattern, and in some cases, cosmetic and functional concerns in adolescence and adulthood. Early identification and appropriate triage are therefore important.
Management
The management of metatarsus adductus is stratified by severity and flexibility. For mild and moderate flexible cases, the initial recommendation is typically observation and parental reassurance, combined with passive stretching exercises. Parents are instructed to gently manipulate the forefoot outward (abduct) during diaper changes and feeding, holding the stretch for several seconds and repeating multiple times throughout the day. The evidence base for stretching alone is variable, but it is generally considered low-risk and may accelerate resolution.
When the deformity is moderate to severe, or when it fails to improve with observation and stretching by around six months of age, serial casting is the intervention of choice. The foot is placed in a corrective cast that gradually abducts the forefoot over a series of weekly or fortnightly cast changes. Serial casting is most effective when initiated before the age of eight months, when the foot bones are still highly malleable. Results are generally excellent, with the majority of treated children achieving a normal or near-normal foot shape.
For rigid cases that do not respond adequately to casting, or for older children presenting with residual deformity, specialised corrective footwear or custom orthotics may be recommended. Surgical intervention is rarely required and is typically reserved for children over four years of age with significant functional impairment. Surgical options include soft tissue releases or osteotomies (surgical realignment of the metatarsal bones), though the long-term outcomes of surgery for MA are mixed, and most paediatric orthopaedic surgeons advocate conservative management wherever possible.
Differential Diagnosis
It is important to distinguish metatarsus adductus from other causes of in-toeing in children, as the management strategies differ considerably. Skewfoot (also called Z-foot or serpentine foot) is a more complex deformity in which both the forefoot and hindfoot are involved, and it carries a less predictable response to conservative treatment. Clubfoot presents with equinus (downward pointing) of the ankle, heel varus, and midfoot cavus in addition to forefoot adduction, and requires prompt, structured management such as the Ponseti method. Internal tibial torsion and femoral anteversion are other common causes of in-toeing that arise from the leg bones rather than the foot itself and require different assessment and treatment pathways.
Metatarsus adductus is a common congenital foot deformity that, in most cases, resolves naturally as the child grows and develops. Its cause is predominantly positional, stemming from intrauterine crowding in the final stages of pregnancy, though genetic factors also play a role. The severity and flexibility of the deformity at presentation guide clinical management, ranging from watchful waiting and parental stretching exercises to serial casting for more rigid or persistent cases. Surgical intervention is an option of last resort. With timely recognition and appropriate management, the prognosis for children with metatarsus adductus is excellent, and the vast majority can expect a fully functional, normally appearing foot in childhood and beyond.