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Adult acquired flatfoot

38 citationsUpdated Sep 2026

Overview

Adult acquired flatfoot deformity is a progressive condition where treatment strategy is dictated by the stage of posterior tibial tendon dysfunction [10]. Initial management prioritizes prompt, aggressive nonsurgical interventions aimed at pain resolution [7, 13]. Surgical correction is reserved for patients with persistent pain or functional limitations who have failed prolonged nonsurgical attempts [4, 7, 13]. In rigid flatfoot deformities, indications for surgery are strict and require documented failure of conservative care [4]. For adolescents, rigid deformities present a less predictable clinical course associated with various underlying causes, making etiological investigation critical for proper management [1]. Diagnostic assessment relies on evaluating the amount of subluxation and incongruence of the middle facet of the subtalar joint, an accurate tool for symptomatic cases [2]. High-resolution cone-beam CT provides measurements analogous to traditional radiographic parameters [3].

Surgical intervention for rigid flatfoot is best proven through osteotomies with supplemental soft-tissue procedures [4]. Both Evans and Hintermann procedures demonstrate good corrective ability for adult acquired flatfoot deformity [8]. In flexible cases, less severe deformities may be appropriately treated with a combined medializing calcaneal osteotomy and flexor digitorum longus transfer, while severe cases might require additional procedures for adequate correction [6]. Tendon transfer arrests the progression of the flat-foot deformity, relieves pain, and restores inversion power of the hind part of the foot, though it does not create a normal medial part of the arch in most patients with posterior tibial tendon rupture [9]. In most patients, calcaneal osteotomy and tendon sling yield a cosmetically acceptable foot with good function [11]. Double calcaneal osteotomy is an effective method for severe adolescent flexible flatfoot and can correct deformities effectively and sustainably, providing symptomatic relief and patient satisfaction [17, 22].

Outcomes are generally favorable, with both flatfoot and non-flatfoot groups demonstrating statistically significant improvements in functional outcomes (VAS and AOFAS) compared to preoperative values following isolated talocalcaneal coalition resection [5]. The relief of pain and restoration of function achieved through effective correction of severe pes planovalgus deformity account for satisfactory outcomes [18]. However, functional outcomes in flatfoot surgery for overcorrected clubfeet are limited by preoperative range of motion and talus deformities [12]. For children with flexible flatfoot, the prognosis for spontaneous increase in arch height and avoidance of long-term pain without treatment is excellent, making the most important aspect of treatment the identification of the entity to permit a change in focus from intervention to education [15]. Concomitant triple C and the modified Kidner procedure result in favorable radiographic and clinical outcomes in the treatment of severe flatfoot associated with a symptomatic accessory navicular in children and adolescents [16]. There is no evidence of progression to valgus flatfoot after tibialis posterior transfer performed to treat central foot drop [19].

Anatomy & Pathophysiology

Definition and Epidemiology

Adult acquired flatfoot deformity (AAFD) is defined by the collapse of the medial longitudinal arch, hindfoot valgus, and midfoot abduction secondary to posterior tibial tendon (PTT) dysfunction [33]. The condition predominantly affects overweight, middle-aged females [33]. Recognized risk factors include obesity, diabetes, hypertension, trauma, and a history of cortisone injections [33]. Subtalar joint orientation may also predispose specific patients to developing AAFD [33]. While flatfoot prevalence reaches 80% in children, it declines to 10% to 20% in adults [31]. Specifically, prevalence drops from 54% in 3-year-olds to 21% in 6-year-olds [31]. Flatfoot is associated with younger age, male sex, ligamentous laxity, and obesity [31]. Tarsal coalitions affect 1 in 100 people and are present bilaterally in 50% of cases [47].

Musculotendinous Anatomy and Biomechanics

The posterior tibial muscle originates from the posterior tibia, fibula, and interosseous membrane [24]. The tendon courses posteriorly and medially around the ankle in a groove adjacent to the medial malleolus, inserting on the midfoot near the navicular tuberosity [24]. Additional bands attach to the plantar cuneiforms, the second through fourth metatarsals, and the sustentaculum tali [24]. The PTT serves as the primary dynamic support for the arch [47]. It fires after the foot is flat to generate heel rise and lock the transverse tarsal joint, creating a rigid, stable platform for push-off [47]. During this phase, the tibia rotates externally as the transverse tarsal locks [47]. The PTT inverts the hindfoot, which locks the transverse tarsal joint to provide a stable platform for gait [33].

The spring (calcaneonavicular) ligament acts as the primary static stabilizer of the talonavicular joint [47]. Its incompetence is associated with increased flatfoot deformity [47]. The superomedial band, originating from the anterior-medial sustentaculum, is the most commonly affected segment [47]. Isolated acute rupture of the spring ligament can cause acute deformity without PTTD [47]. Biomechanical data identifies the tibiospring ligament (medial malleolus to navicular) as the most relevant structure for decreasing abduction [47].

The gastrocnemius complex is frequently contracted in AAFD [47]. Triceps surae contracture is a common concomitant of flatfoot associated with poorer outcomes [40]. Excessive tensile forces from the triceps surae cause valgus displacement of the calcaneus under the talus [40]. This displacement results in increased dorsal flexion at the subtalar joint rather than the tibio-talar joint [40].

Pathophysiology and Progression

PTTD etiology is multifactorial, involving a hypovascular zone 2 to 6 cm proximal to the PTT insertion on the navicular [47]. Contributing factors include arch overload from activity or obesity, and inflammatory disorders such as rheumatoid arthritis [47]. When the PTT degenerates, the hindfoot falls into valgus, stressing medial static stabilizers including the spring ligament [33]. Spring ligament incompetence causes lateral translation of the navicular, resulting in medial talar head uncoverage and midfoot abduction [33]. Progressive valgus stress may lead to deltoid ligament incompetence, talar tilt, and ankle arthritis [33]. A gastrocnemius contracture develops as the axis of pull shifts laterally, further exacerbating valgus alignment [33].

The main characteristic of idiopathic pes planovalgus is laxity of the subtalar and transverse talar joints, sometimes combined with excessive length of the tibialis posterior muscle [40]. The primary feature is the exacerbation of the physiological uncoiling of the calcaneo-pedal unit helix, involving calcaneal pronation (valgus), forefoot supination, and internal rotation of the talo-tibio-fibular unit [40]. This uncoiling explains the collapse of the medial column [40]. In children, midfoot and forefoot supination may involve a length discrepancy between columns, leading to abduction [40]. Rigid flatfoot deformities in adolescents have a less predictable clinical course and various underlying causes [1]. Tendon transfer does not create a normal medial arch in most patients but arrests progression, relieves pain, and restores hindfoot inversion power [9].

Clinical Presentation and Physical Examination

Patients with AAFD present with medial ankle pain and gait dysfunction [33]. As the disease progresses, lateral ankle pain may develop due to subfibular impingement [33]. Early complaints include medial ankle/foot pain and progressive arch loss, while late complaints involve lateral ankle pain from subfibular impingement [42]. Physical examination reveals tenderness over the PTT [33]. Standing evaluation from behind demonstrates valgus alignment [33]. Standing examination also shows asymmetric hindfoot valgus, depressed arch, and an abducted forefoot [42]. The "too-many-toes sign" is observed when viewing the foot posteriorly, appearing to show more than five toes [42].

Functional assessment relies on the single-limb heel rise. If the patient can perform the heel rise and the hindfoot inverts as the heel elevates, the PTT remains functional and the deformity is flexible [33]. If the hindfoot does not invert, the deformity is rigid [33]. Pain or inability to perform a single-limb heel rise indicates insufficient PTT [42]. Gastrocnemius contracture is assessed using the Silfverskiold test, ensuring the hindfoot is inverted out of valgus during examination [33]. Lateral impaction syndrome or subfibular impingement may be present when significant heel valgus causes abutment against the fibula [42]. Abutment of the lateral process of the talus and the calcaneus can also occur [42].

In flexible flatfoot, hindfoot valgus and loss of the medial longitudinal arch are evident when standing [31]. The talar head may be palpable medially due to its plantarflexed position [31]. Uncovering of the navicular and associated calluses may be present [31]. The hindfoot exhibits full passive motion with inversion and eversion [31]. With toe rise, the arch is restored and the hindfoot rolls into varus to lock the transverse tarsal joints [31]. Many patients with flexible flatfoot are asymptomatic and are evaluated due to parental concerns about appearance [31]. Symptomatic patients may report medial arch pain, calf pain from contracture, or lateral sinus tarsi pain from calcaneofibular abutment [31].

The heel shows excessive eversion during weight bearing, and the forefoot is usually abducted, producing a midfoot sag with lowering of the longitudinal arch [14]. The talar head and navicular tuberosity appear to contact the floor and participate excessively in weight bearing [14]. The medial column appears longer than the lateral column [14]. Although the foot is often described as pronated, this is misleading because the forefoot is actually supinated relative to the hindfoot [14]. This relationship is best appreciated by contemplating a cavovarus foot, the anatomic reverse of flatfoot, where the forefoot is pronated relative to the hindfoot and the arch is excessively high [14].

Flatfoot refers to the loss of the normal longitudinal arch of the medial foot [26]. Many cases are inherited, and a careful family history may uncover other affected individuals [26]. The foot is usually flexible, so the arch appears when not bearing weight [26]. Hindfoot valgus (heel eversion) is often present [26]. In severe cases, flatfoot may be painful, though this aspect is often overemphasized [26]. Subtalar motion is usually normal in flexible flatfoot [26]. When standing on tiptoe, a normal arch and varus heel are frequently disclosed by muscle action in feet that show a flat arch and valgus heel while standing [26]. If signs of flexible flatfoot are absent, alternative diagnoses such as tarsal coalition should be considered [26]. The physician should look for painful plantar calluses [26].

When assessing children, the examiner must consider age because underlying conditions are age-specific [25]. Infants may have simple positional deformity, medial arch fat pads obscuring the arch, calcaneovalgus foot, or congenital rocker bottom foot (vertical talus) [25]. Young children most likely have flexible flatfoot deformity [25]. The most common type seen by pediatric orthopaedists is flexible flatfoot deformity of childhood, typically in children between 18 months and 6 years of age [25]. This condition is painless, with supple range of motion and arch reconstitution during toe-walking or non-weight-bearing [25]. Most flexible flatfeet resolve spontaneously without residual adverse effects; surgery is rarely indicated [25].

Adolescents may present with a tight heel cord with secondary midfoot breakdown or posterior spastic flatfoot caused by tarsal coalition or other problems [25]. Pain not related to exercise may indicate inflammatory arthritis, infection, or rarely a bone lesion [25]. Nonspecific foot, ankle, or lower leg pain in adolescents may be caused by tarsal coalition [25]. Congenital vertical talus is characterized by fixed flattening of the longitudinal arch, tight heel cord, variable pain, and usually a palpable dorsolateral dislocation of the navicular on the talus [25]. Classic symptomatic tarsal coalition presents with fixed flattening of the longitudinal arch, fixed hindfoot valgus, and nonspecific or exercise-induced pain [25]. During rapid passive inversion of the subtalar joint, patients with tarsal coalition may experience peroneal muscle spasm [25]. During gait, the foot appears externally rotated and inflexible, as if wearing a short-leg walking cast [25]. Patients with tarsal coalition are typically between 8 years and adolescence [25]. Patients with midfoot breakdown secondary to a tight heel cord may present at any age after walking [25]. The longitudinal arch may or may not reconstitute in the non-weight-bearing position in this condition [25]. The cause of the tight heel cord (e.g., static encephalopathy, tethered cord, idiopathic) should be sought by further examination [25].

Radiographic and Imaging Parameters

A standing lateral radiograph allows measurement of the lateral talus–first metatarsal angle, or Meary angle [14]. The normal Meary angle is 0 degrees (a straight line) [14]. In flexible flatfoot, an apex-plantarward angle is present [14]. The normal range varies with age, with spontaneous improvement in plantar sag seen until age 8 years [14]. The location of the sag—talonavicular or naviculocuneiform joint—can be determined and may suggest the cause of an abnormal measurement [14]. A tight heel cord producing a plantarflexed talus and talonavicular sag can be suggested by the location of the sag [14]. The degree of plantar flexion of the talus, measured as the angle between the longitudinal axis of the talus and the horizontal, has a normal value of 26.5 ± 5.3 degrees [14]. The calcaneal pitch angle, formed by the axis of the calcaneus and the horizontal, can also be measured [14]. Perhaps the most compelling reason to obtain radiographs in flatfoot is to rule out causes other than idiopathy [14]. The differential diagnosis includes bony abnormalities such as tarsal coalition, congenital vertical talus (convex pes valgus), persistent talipes calcaneovalgus, an accessory navicular, and various arthritic and inflammatory conditions [14]. Most of these conditions are diagnosed primarily from history and physical examination, with radiographs used to confirm a suspected diagnosis [14].

Standing radiographs disclose loss of the normal medial longitudinal arch and may show mild lateral subluxation of the talonavicular joint [26]. In severe chronic cases, degenerative talonavicular spurring may be present [26]. Radiographs should be obtained only if the patient is symptomatic [31]. Weight-bearing AP, lateral, and oblique views are used to evaluate for other potential sources of the planovalgus deformity [31]. On the AP view, the talar head may appear uncovered, and the amount of talonavicular coverage is related to the onset of symptoms [31]. On lateral radiographs, the talar declination angle is increased, as is the Meary angle [31]. Decreased calcaneal pitch may be observed in patients with Achilles tendon contracture [31].

Weight-bearing radiographs of the foot and ankle are evaluated for degree of deformity and degenerative changes in AAFD [33]. Arch collapse is quantified by measuring Meary’s angle on the lateral view [33]. Percentage uncoverage of the talar head on the AP foot radiograph is measured [33]. A hindfoot alignment radiograph may be useful to measure hindfoot moment arm, which can predict the amount of intraoperative deformity correction required [33]. Ankle radiographs should always be performed to assess for valgus talar tilt [33]. MRI may demonstrate degeneration in the PTT and spring ligament injury; however, it is not a requisite preoperative study in the presence of significant deformity [33].

Pes planus is indicated by a negative lateral talar–first metatarsal angle (Meary angle) [42]. Forefoot abduction is indicated by TN uncoverage [42]. A talar–first metatarsal angle greater than 4 degrees signifies pes planus [45]. The calcaneal pitch angle is determined on the lateral radiograph; a normal angle is between 17 and 32 degrees [45]. Arch height loss is documented by a decrease in the calcaneal pitch angle [45]. A loss of medial cuneiform–floor height is also indicative of loss of arch height [45]. Tarsal coalitions may be diagnosed by seeing a C-sign/dorsal talar beaking on x-ray (middle facet coalition) [47]. An elongated anterior process of calcaneus on the lateral radiograph indicates calcaneonavicular coalition [47].

Classification Systems

The most common classification system for AAFD is based on the degree of deformity [33]. Stage I is tendinopathy of the posterior

Classification

Myerson (adapted from Johnson & Strom): This system classifies adult acquired flatfoot deformity (AAFD) based on the degree of deformity [33]. Stage I is defined as posterior tibial tendinopathy with minimal underlying deformity [33]. Stage II is characterized by a flexible deformity with talar head uncoverage seen on the weight-bearing AP foot radiograph [33]; talar head uncoverage of greater than 30% differentiates between a stage IIa and IIb deformity [33]. Stage III is defined as a rigid deformity due to arthritis in the hindfoot [33]. Stage IV indicates ankle joint involvement [33].

Johnson & Strom (adapted by Myerson): This classification details specific clinical and radiographic findings across four stages. Stage 1 is characterized by medial pain, orthograde hindfoot, orthograde middlefoot, and a possible single heel rise [60]. Stage 2 is characterized by medial pain, valgus flexible hindfoot, orthograde or abducted middlefoot, and a weakened single heel rise [60]. Stage 3 is characterized by medial and lateral hindfoot pain, valgus contracted hindfoot, abducted middlefoot, and an impossible single heel rise [60]. Stage 4 is characterized by general hindfoot pain, valgus contracted hindfoot, abducted middlefoot, and an impossible single heel rise [60].

Müller-Weiss Disease Classifications: Two classification systems have been proposed for Müller-Weiss disease (MWD) [23]. Maciera and Rochera: This system describes five stages of increasing deformity for MWD, ranging from minimal change to talocuneiform articulation [23]. Wong-Chung et al.: This system describes three main groups for MWD based on various radiographic features [23]. Neither the Maciera and Rochera nor the Wong-Chung classification systems for MWD are useful for guiding clinical management or predicting prognosis [23].

Clinical Presentation

History and General Presentation

Adult acquired flatfoot deformity (AAFD) is characterized by collapse of the medial longitudinal arch, hindfoot valgus, and midfoot abduction related to dysfunction of the posterior tibial tendon [33]. Patients commonly present with medial ankle pain and gait dysfunction related to this deformity [33]. In children with flexible flatfoot, the prognosis for spontaneous increase in arch height and avoidance of long-term pain without treatment is excellent [15]. Symptomatic patients with flexible flatfoot may report medial arch pain, calf pain caused by contracture, and/or lateral sinus tarsi pain caused by calcaneofibular abutment [31]. In severe cases of flatfoot, the foot may be painful, but this aspect of the deformity is often overemphasized [26]. Pain that is not related to exercise in children may be caused by inflammatory arthritis, infection, or, rarely, a bone lesion [25].

Physical Examination: Inspection and Palpation

The examination of the feet starts by having the patient walk and observing whether the gait pattern is normal, antalgic, or indicative of neuromuscular dysfunction [25]. Standing evaluation from behind the patient with AAFD demonstrates valgus alignment [33]. The patient’s foot should be examined from behind because it is easier to assess hindfoot valgus from this position [25]. Standing examination of flatfoot deformity demonstrates asymmetric hindfoot valgus, depressed arch, and an abducted forefoot [42]. The "too-many-toes sign" is observed when the foot is viewed posteriorly and appears to have more than five toes due to excessive forefoot abduction [42]. In flexible flatfoot, the talar head may be palpable medially because of its plantarflexed position [31]. On examination of AAFD, there is tenderness over the posterior tibial tendon [33]. The physician should look for painful plantar calluses during the physical examination of flatfoot [26].

Physical Examination: Range of Motion and Stability

The child should be asked to heel-walk, toe-walk, and hop on each foot in turn to assess neurologic and musculoskeletal function [25]. If the longitudinal arch is absent when the patient is standing still, the examiner should look for reconstitution of the arch when the patient is walking on the toes [25]. Reconstitution of the longitudinal arch can be assessed by having the patient stand on the toes [25]. The examiner should note whether the hindfoot swings from valgus to varus [25]. If the hindfoot stays in valgus, tarsal coalition may be present [25]. Passive range of motion should be checked with the patient sitting to rule out the presence of a tight heel cord [25]. A tight heel cord, regardless of cause, can lead to flatfoot because of compensatory midfoot breakdown [25]. Rocking the subtalar joint into inversion and eversion should be performed, and any stiffness or peroneal muscle spasm suggests the presence of tarsal coalition or possibly inflammatory arthritis [25]. During rapid passive inversion of the subtalar joint in a patient with tarsal coalition, the patient may experience peroneal muscle spasm [25]. During gait, a patient with tarsal coalition will have an externally rotated, inflexible foot, as if the patient were wearing or had just come out of a short-leg walking cast [25]. The longitudinal arch in patients with midfoot breakdown secondary to a tight heel cord may or may not reconstitute when the foot is in the non-weight-bearing position [25]. The cause of the tight heel cord itself should be sought by further examination, including static encephalopathy, tethered cord or other intrathecal anomaly, or idiopathic causes [25].

In flexible flatfoot, the hindfoot shows full passive motion with inversion and eversion [31]. With toe rise in flexible flatfoot, the arch is restored and the hindfoot rolls into varus to lock the transverse tarsal joints [31]. The foot with flexible flatfoot will have supple range of motion on examination and the longitudinal arch will readily reconstitute during toe-walking or when the foot is in a non-weight-bearing position [25]. The foot in flatfoot is usually flexible, so the arch appears when the foot is not bearing weight [26]. Physical determination of the flexibility of flatfoot requires careful examination, and subtalar motion is usually normal [26]. The range of motion of the tibiotalar joint should be tested in patients with flexible flatfoot [31]. The entire limb should be inspected for rotational malalignment in patients with flexible flatfoot [31].

Special Tests and Red Flags

If the patient is able to perform a single-limb heel rise and the hindfoot inverts as the heel elevates, the posterior tibial tendon remains functional and the deformity is considered flexible [33]. Pain or inability to perform a single-limb heel rise indicates insufficient posterior tibial tendon [42]. The presence of a gastrocnemius contracture is assessed with the Silfverskiöld test, making sure to invert the hindfoot out of valgus during examination [33]. The Silfverskiöld test should be performed in patients with flexible flatfoot because the condition often is associated with Achilles tendon or gastrocnemius contracture [31]. Lateral impaction syndrome or subfibular impingement may be present with significant valgus of the heel such that it abuts the fibula [42]. Abutment of the lateral process of the talus and the calcaneus can occur in flatfoot deformity [42]. An adolescent may have a tight heel cord with secondary midfoot breakdown or a posterior spastic flatfoot caused by tarsal coalition [25].

Radiographic and Imaging Findings

Arch collapse in AAFD is quantified by measuring Meary’s angle on the lateral view [33]. Percentage uncoverage of the talar head on the AP foot radiograph is measured in AAFD [33]. A hindfoot alignment radiograph may be useful to measure hindfoot moment arm, which can predict the amount of intraoperative deformity correction required in AAFD [33]. Ankle radiographs should always be performed to assess for valgus talar tilt in AAFD [33]. MRI may demonstrate degeneration in the posterior tibial tendon and spring ligament injury in AAFD [33]. MRI is not a requisite preoperative study in the presence of significant deformity in AAFD [33].

Pes planus is indicated by a negative lateral talar–first metatarsal angle (Meary angle) on radiographs [42]. Forefoot abduction is indicated by talonavicular uncoverage on radiographs [42]. Standing radiographs disclose loss of the normal medial longitudinal arch and may show mild lateral subluxation of the talonavicular joint in flatfoot [26]. In severe chronic cases of flatfoot, degenerative talonavicular spurring may be present on standing radiographs [26]. Radiographs should be obtained only if the patient with flexible flatfoot is symptomatic [31]. Weight-bearing AP, lateral, and oblique views are used to evaluate for other potential sources of the planovalgus deformity in flexible flatfoot [31]. On the AP view of flexible flatfoot, the talar head may appear uncovered [31]. The amount of talonavicular coverage has been shown to be related to the onset of symptoms in flexible flatfoot [31]. On lateral radiographs of flexible flatfoot, the talar declination angle is increased [31]. On lateral radiographs of flexible flatfoot, the Meary angle (the angle between the first metatarsal and the axis of the talus) is increased [31]. Decreased calcaneal pitch may be observed in patients with flexible flatfoot who have contracture of the Achilles tendon [31]. In a flexible flatfoot, an apex-plantarward angle will be present on the Meary angle measurement [14]. The location of the sag—talonavicular or naviculocuneiform joint—can be determined by radiographs and may suggest the cause of an abnormal measurement [14]. A tight heel cord can produce a plantar flexed talus and talonavicular sag [14]. The calcaneal pitch angle, which is formed by the axis of the calcaneus and the horizontal, can also be measured [14]. Most conditions in the differential diagnosis of flatfoot are diagnosed primarily from the history and physical examination findings [14]. Radiographs should be used to confirm a suspected diagnosis in cases of flatfoot where the cause is identified by history and physical examination [14]. The TMTInd as a combination of TMTIB and TMT-lat has been shown to be reliable and valuable to distinct normal feet from flatfeet [36]. A simple footprint assessment board has been validated for diagnosing the severity of flatfoot [21].

Classification

Stage I: Tendinopathy of the posterior tibial tendon in the absence of significant deformity [33]. Stage IIa: Defined as less than 30% talonavicular uncoverage [33]. Stage IIb: Defined as greater than 30% talonavicular uncoverage; talar head uncoverage of greater than 30% differentiates between a stage IIa and IIb deformity [33]. Stage III: A rigid deformity due to arthritis in the hindfoot, characterized by no hindfoot inversion with single-limb heel rise and deformity that is not passively correctable [33]. Stage IV: Characterized by talar tilt and/or valgus ankle arthritis due to long-standing foot deformity [33].

In severe pes planovalgus deformity, the relief of pain and the restoration of function achieved through effective correction account for the satisfactory outcomes [18].

Investigations

Clinical Examination

Physical examination begins with observation of gait patterns, heel-walking, toe-walking, and hopping to assess neurologic and musculoskeletal function [25]. Reconstitution of the longitudinal arch during toe-walking or in a non-weight-bearing position distinguishes flexible flatfoot from rigid deformities [25]. The single-limb heel rise test determines deformity flexibility; if the hindfoot inverts as the heel elevates, the posterior tibial tendon (PTT) is functional and the deformity is flexible, whereas a lack of inversion indicates a rigid deformity [33]. The Silfverskiold test assesses for gastrocnemius contracture, requiring the hindfoot to be inverted out of valgus during the examination [33].

In severe flatfoot, the talar head and navicular tuberosity appear to contact the floor and participate excessively in weight bearing [14]. The forefoot is typically abducted, producing a midfoot sag with lowering of the longitudinal arch [14]. The medial column of the foot appears longer than the lateral column [14]. Describing the entire foot as "pronated" is misleading because the forefoot is actually supinated in relation to the hindfoot [14]. Stiffness or peroneal muscle spasm during passive inversion and eversion of the subtalar joint suggests tarsal coalition or inflammatory arthritis [25]. A fixed flattening of the longitudinal arch combined with fixed hindfoot valgus and nonspecific or exercise-induced pain is characteristic of symptomatic tarsal coalition [25]. Congenital vertical talus is characterized by a fixed flattening of the longitudinal arch, a tight heel cord, variable pain, and a palpable dorsolateral dislocation of the navicular on the talus [25].

Pain not related to exercise may indicate inflammatory arthritis, infection, or a bone lesion [25]. Nonspecific foot, ankle, or lower leg pain in adolescents or preadolescents may be caused by tarsal coalition [25]. Patients with tarsal coalition typically present between the ages of 8 years and adolescence [25]. The most common type of flatfoot seen in pediatric orthopaedics is flexible flatfoot deformity, which is typically painless and occurs in children between 18 months and 6 years of age [25].

Radiographic Assessment

Weight-bearing radiographs of the foot and ankle are evaluated to determine the degree of deformity and degenerative changes [33]. Arch collapse is quantified by measuring Meary’s angle on the lateral weight-bearing radiograph, with a normal range of 0 to 10 degrees [33]. The percentage of talar head uncoverage is measured on the anteroposterior (AP) weight-bearing foot radiograph, with a normal range of 0 to 30% [33]. A hindfoot alignment radiograph measures the hindfoot moment arm, which can predict the amount of intraoperative deformity correction required [33]. Ankle radiographs assess for valgus talar tilt, which may occur due to long-standing deformity and deltoid ligament insufficiency [33].

The normal calcaneal pitch angle is between 17 and 32 degrees [45]. Loss of medial cuneiform–floor height is indicative of loss of arch height [45]. The calcaneal pitch angle is formed by the axis of the calcaneus and the horizontal [14]. The degree of plantar flexion of the talus is measured as the angle formed by the longitudinal axis of the talus and the horizontal, with a normal value of 26.5 ± 5.3 degrees [14]. Standing radiographs may show mild lateral subluxation of the talonavicular joint and, in severe chronic cases, degenerative talonavicular spurring [26]. The location of the sag—talonavicular or naviculocuneiform joint—can be determined on radiographs and may suggest the cause of an abnormal measurement [14].

Radiographs are used to rule out causes of flatfoot other than idiopathy, including tarsal coalition, congenital vertical talus, persistent talipes calcaneovalgus, accessory navicular, and arthritic or inflammatory conditions [14]. The C-sign or dorsal talar beaking on x-ray is a diagnostic indicator for middle facet coalition [47]. An elongated anterior process of the calcaneus on the lateral radiograph is a diagnostic indicator for calcaneonavicular coalition [47]. The TMTInd, a combination of TMTIB and TMT-lat, is reliable and valuable for distinguishing normal feet from flatfeet in juvenile flatfoot deformity [36].

Advanced Imaging

MRI may demonstrate degeneration in the posterior tibial tendon and injury to the spring ligament [33]. MRI is not a requisite preoperative study in the presence of significant deformity [33]. CT scans are used in the diagnostics of flatfoot deformity, particularly for identifying tarsal coalitions [47].

Treatment

Non-Operative

Symptomatic management with shoe modifications, arch supports, and plantar inserts is appropriate for flatfoot because no long-term treatment can alter the anatomic features of the disorder [26]. Nonsurgical measures constitute the initial treatment choice for flexible flatfoot, beginning with an explanation of the natural history of the condition to both the patient and the family [31]. In patients with flexible flatfoot and arch pain, a navicular pad, medial arch support, or a University of California Biomechanics Laboratory orthotic may help with symptoms but will not correct the deformity or prevent progression in patients who are asymptomatic [31]. Patients with contractures of the Achilles tendon or gastrocnemius muscle associated with flexible flatfoot should begin a stretching program to decrease associated calf pain [31].

Operative

Indications: In the few patients with flexible flatfoot in whom prolonged nonsurgical measures fail, consideration can be given to lateral column lengthening through a calcaneal lengthening osteotomy or a combined calcaneal-cuboid-cuneiform osteotomy [31]. Operative treatment showed better results compared to nonoperative treatment in children with painful rigid flatfoot and talocalcaneal coalition [63]. Triple arthrodesis is rarely appropriate and should be performed only according to specific indications [58].

Surgical Approach / Technique: Severe acquired flexible flatfoot might require an additional procedure beyond medializing calcaneal osteotomy and flexor digitorum longus transfer for adequate correction [6]. Double calcaneal osteotomy was an effective method for severe adolescent flexible flatfoot with additional procedures [17]. In most patients, calcaneal osteotomy and tendon sling for the management of calcaneus deformity yielded a cosmetically acceptable foot with good function [11]. Both H-LCL and E-LCL osteotomies provide outstanding radiographic correction and significant enhancement of clinic scores in flatfoot deformity [34]. Posterior tibial advancement, subtalar joint elevation or fusion, and elongation osteotomy of the lateral calcaneal neck are surgical options for flatfoot but may not provide reproducible, predictable resolution of the problem [26].

Other Considerations: Gastrocnemius recession may be simultaneously considered to manage the associated equinus deformity during surgical intervention for flexible flatfoot [31]. The relief of pain and the restoration of function achieved through effective correction of severe pes planovalgus deformity account for satisfactory outcomes in complex reconstruction [18].

Complications

Other Considerations: Tendon transfer procedures do not create a normal medial part of the arch in most patients [9]. Functional outcomes are limited by preoperative range of motion and talus deformities [12]. There is a noticeable tendency toward the overcorrection of the deformity, as evidenced by increased pressure exerted on the lateral midfoot [29].

Recovery

Light activity (weeks): The evidence base does not specify a typical week range for the resumption of desk work, driving, or light activities of daily living.

Full activity (months): The provided evidence does not define a specific month range for the return to manual work, sport, or full range of motion and strength.

Complete recovery / outcome plateau (months): The evidence does not establish a specific month range for the stabilization of pain, strength, and final functional outcomes.

Rehabilitation protocol: No specific physiotherapy phasing, immobilisation duration, weight-bearing progression, or brace removal timing is detailed in the current evidence.

Functional milestones: Validated patient-reported outcome measure trajectories are not specified. However, effective correction of severe pes planovalgus deformity achieves satisfactory outcomes through the relief of pain and restoration of function [18]. Tendon transfer relieves pain [9] and restores inversion power of the hind part of the foot [9]. Double calcaneal osteotomy provides symptomatic relief and patient satisfaction [22].

Other Considerations: Tendon transfer arrests the progression of the flat-foot deformity [9]. Double calcaneal osteotomy corrects flatfoot deformities effectively and sustainably [22]. In overcorrected clubfeet following extensive surgery, functional outcomes are limited by preoperative range of motion and talus deformities [12]. Regarding subtalar extra-articular screw arthroereisis for juvenile flexible flatfoot, the contact area normalizes within 4 weeks post-operation [49]; however, the medial midfoot contact area remains reduced at 28 days [49].

Key Evidence

• [L5] Rigid flatfoot deformities in adolescents have a less predictable clinical course and are associated with various underlying causes, making it critical to investigate the etiology to recommend proper management. [1] (10.5435/jaaos-d-21-00448)
• [L3] The assessment of the amount of subluxation and incongruence of the middle facet of the subtalar joint represents an accurate diagnostic tool for symptomatic adult acquired flatfoot deformity. [2] (10.2106/jbjs.19.00073)
• [L2] Measurements analogous to traditional radiographic parameters of adult acquired flatfoot deformity are obtainable using high-resolution cone-beam CT. [3] (10.2106/jbjs.16.01366)
• [L4] Indications for surgery are strict, requiring failure of prolonged nonsurgical attempts to relieve pain, and osteotomies with supplemental soft-tissue procedures are the best proven approach for management of rigid flatfoot. [4] (10.5435/jaaos-22-10-623)
• [L4] Both flatfoot and non-flatfoot groups demonstrated statistically significant improvements in functional outcomes (VAS and AOFAS) compared to preoperative values. [5] (10.1186/s12891-026-09801-1)
• [L5] Less severe acquired flexible flatfoot might be appropriately treated with a combined medializing calcaneal osteotomy and flexor digitorum longus transfer, while severe flatfoot might require an additional procedure for adequate correction. [6] (10.2106/jbjs.e.00045)
• [L5] Prompt early, aggressive nonsurgical management is important, and patients in whom such treatment fails should strongly consider surgical correction to avoid worsening of the deformity. [7] (10.5435/00124635-200807000-00005)
• [L3] Both Evans and Hintermann procedures have good corrective ability for adult acquired flatfoot deformity. [8] (10.1186/s13018-024-04584-4)
• [L4] Tendon transfer does not create a normal medial part of the arch in most patients, but our method arrests the progression of the flat-foot deformity, relieves pain, and restores inversion power of the hind part of the foot. [9] (10.2106/00004623-198567090-00027)
• [L5] For ankle osteoarthrosis, total ankle replacement demonstrates superior gait mechanics compared to arthrodesis, while adult acquired flatfoot deformity treatment depends on the stage of posterior tibial tendon dysfunction. [10] (10.1302/2058-5241.1.000015)
• [L4] In most patients, the operation yielded a cosmetically acceptable foot with good function. [11] (10.2106/00004623-198971080-00011)
• [L4] Functional outcomes are limited by preoperative range of motion and talus deformities. [12] (10.1007/s00402-018-2932-y)
• [L5] Adult acquired flatfoot deformity (AAFD) is commonly treated with nonsurgical methods for pain resolution, while surgical interventions are reserved for patients with persistent pain or functional limitations. [13] (10.5435/jaaos-d-21-00008)
• [L5] The prognosis for spontaneous increase in arch height and avoidance of long-term pain without treatment is excellent for children with flexible flatfoot; therefore, the most important aspect of treatment is identification of the entity to permit a change in focus from intervention to education. [15] (10.2106/00004623-199512000-00021)
• [L4] Concomitant triple C and the modified Kidner procedure result in favorable radiographic and clinical outcomes in the treatment of severe flatfoot associated with a symptomatic accessory navicular in children and adolescents. [16] (10.1186/s13018-014-0131-2)
• [L4] With additional procedures, double calcaneal osteotomy was an effective method for severe adolescent flexible flatfoot. [17] (10.1186/s13018-017-0655-3)
• [L4] The relief of pain and the restoration of function achieved through effective correction of the severe pes planovalgus deformity account for the satisfactory outcomes. [18] (10.2106/00004623-199911000-00006)
• [L4] In contrast to the working hypothesis, we found no evidence of progression to valgus flatfoot after TPT transfer performed to treat central foot drop. [19] (10.1016/j.otsr.2018.11.013)
• [L2] [21] (10.1186/s12891-021-04154-3)
• [L4] Double calcaneal osteotomy could be used to correct flatfoot deformities effectively and sustainably and provide symptomatic relief and patient satisfaction. [22] (10.1186/s13018-024-05106-y)
• [L5] [23] (10.5435/jaaosglobal-d-24-00402)
• [L5] [24] (10.5435/00124635-199903000-00004)
• [L3] Furthermore, our findings highlight a noticeable tendency toward the overcorrection of the deformity, as evidenced by increased pressure exerted on the lateral midfoot. [29] (10.2106/jbjs.24.00394)
• [L3] Both H-LCL and E-LCL osteotomies provide outstanding radiographic correction and significant enhancement of clinic scores in flatfoot deformity. [34] (10.1186/s12891-025-08678-w)
• [L3] The TMTInd as a combination of TMTIB and TMT-lat has been shown to be reliable and valuable to distinct normal feet from flatfeet. [36] (10.1186/s12891-020-03854-6)
• [L4] [40] (10.1016/j.otsr.2018.03.010)
• [Paper] The contact area normalizes within 4 weeks, although the medial midfoot contact area remains reduced at 28 days. [49] (10.1007/s00402-019-03230-7)
• [L4] Triple arthrodesis is rarely appropriate and should be performed only according to specific indications. [58] (10.2106/00004623-199303000-00004)
• [L4] [60] (10.1007/s00402-015-2295-6)
• [L3] The operative treatment showed better results compared to the nonoperative treatment. [63] (10.1186/s12891-020-03213-5)

References

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