Your teenager used to run without a second thought. Over the past year, the outside and middle of one foot started aching after football, netball, or a long day of CCA. The foot looks flat, and unlike a younger child’s flat foot, it does not spring back into an arch when they go up on tiptoe. They have rolled the same ankle more than once, and each sprain seems to come easier than the last. Ordinary sprain rehab settles things briefly, then the pain returns with activity. This pattern, a stiff flat foot that started hurting somewhere between ages 8 and 14, is the classic way a tarsal coalition announces itself.
A tarsal coalition is an abnormal bridge between two of the tarsal bones at the back and middle of the foot. The bridge can be made of bone, cartilage, or fibrous tissue, and it most often links the heel bone to the navicular (a calcaneonavicular coalition) or the heel bone to the talus (a talocalcaneal coalition). The bridge is present from birth but is usually soft and painless in early childhood. As it hardens with growth, it locks the joints that normally let the hindfoot swivel and adapt to the ground, which is why the foot becomes rigid and starts to ache. Because the pain often shows up as “just another sprain” or “flat feet”, the coalition is frequently missed for months. Accurate diagnosis matters because a rigid painful flatfoot is managed very differently from a flexible one, and imaging is usually needed to confirm it.
Symptoms of Tarsal Coalition
Tarsal coalition rarely causes trouble until the bridge begins to ossify, so symptoms typically appear in later childhood and adolescence rather than in toddlers. The combination of a rigid flat foot and activity-related pain in this age group is the most useful early signal.
- A flat foot that stays flat: the arch does not reappear when the child stands on tiptoe or when the foot is off the ground. This rigidity is the single feature that most separates a coalition from an ordinary flexible flat foot.
- Aching midfoot or lateral foot pain with activity: the pain builds with running, jumping, and sport, and eases with rest. It commonly sits around the middle or outer part of the foot, below the ankle.
- Recurrent ankle sprains on the same side: the stiff hindfoot cannot absorb uneven ground, so the ankle gives way repeatedly. Parents often describe an ankle that “keeps rolling” despite rehab.
- Peroneal muscle spasm: the muscles on the outside of the leg tighten to guard the restricted joints, holding the foot turned outward. This is sometimes called a peroneal spastic flatfoot.
- Reduced side-to-side hindfoot motion: when the heel is gently moved, its inward and outward swivel is noticeably limited compared with the other foot.
- Pain over the coalition itself: pressing just below and in front of the inner ankle bone, or over the outer midfoot, can reproduce the tenderness depending on which joint is bridged.
- Symptom onset between ages 8 and 14: calcaneonavicular coalitions tend to become symptomatic around 8 to 12, talocalcaneal ones a little later around 12 to 15, matching the age each bridge hardens.
From what we see in clinic, the most reliable clue is the pairing of a foot that will not form an arch on tiptoe with activity pain in an older child. A flexible flat foot that forms an arch on tiptoe rarely behaves this way.
Causes of Tarsal Coalition
A tarsal coalition is a developmental condition, not something a child does to their foot. It forms early and only becomes noticeable later.
What Causes Tarsal Coalition?
- A failure of segmentation before birth: during early development the tarsal bones normally separate into distinct bones with joints between them. In a coalition, two bones fail to fully divide, leaving a bridge of bone, cartilage, or fibrous tissue between them.
- Progressive ossification with growth: the bridge starts soft and flexible, then gradually hardens through late childhood. As it stiffens, it removes the give in the joints and the foot turns rigid and symptomatic.
- Activity that loads a stiffening joint: the coalition does not appear because of sport, but rising training loads through the school years often unmask a bridge that was previously silent, which is why symptoms so often start in an active teenager.
- Acquired coalitions (uncommon): rarely, a bridge forms after significant trauma, infection, previous surgery, or inflammatory joint disease rather than from birth. These are the exception, not the usual paediatric picture.
Who Carries a Higher Baseline Risk?
- Children and adolescents between roughly 8 and 15, when the bridge typically hardens.
- Children with a family history, since coalitions can run in families.
- Active children in running, jumping, and court sports, who load the hindfoot heavily and tend to notice the stiffness sooner.
- Children who have had repeated ankle sprains on the same foot without a clear cause.
- Both feet can be affected in a proportion of children, so a coalition in one foot warrants a look at the other.
Conditions Commonly Mistaken for Tarsal Coalition
A rigid, aching flat foot in an older child overlaps with several other conditions that share the same territory. Sorting them apart usually needs a hands-on assessment of how much the hindfoot actually moves, supported by imaging. The most common patterns of confusion are below.
Flexible flat feet in children
Flat feet in children are common, usually painless, and flexible, meaning the arch reappears when the child stands on tiptoe or sits. A tarsal coalition looks similar at a glance but stays flat in every position and hurts with activity. The tiptoe test is the quick bedside differentiator: a flexible flat foot forms an arch, a coalition does not. The same distinction applies to adult flexible adult flatfoot that carries over from childhood.
Recurrent ankle sprains and chronic ankle instability
Because a coalition makes the ankle give way, it is easily labelled as ordinary recurrent ankle sprains or chronic ankle instability. The difference is that a coalition also restricts hindfoot motion and produces a rigid flat foot, whereas instability from ligament laxity leaves the foot flexible. An ankle that keeps rolling and a foot that will not swivel or arch is a reason to look for a coalition behind the sprains.
Accessory navicular
An accessory navicular is an extra bone on the inner arch that can cause a tender bump and inner foot pain in the same age group, sometimes alongside a flat foot. The pain of an accessory navicular localises to the prominent inner bump, while a talocalcaneal coalition sits deeper below the inner ankle and restricts hindfoot movement. Both can produce a painful adolescent flat foot, so imaging often settles which is driving the symptoms.
Peroneal tendonitis
Peroneal tendonitis irritates the tendons running around the outer ankle and can mimic the lateral foot pain of a coalition. The peroneal spasm that a coalition produces adds to the confusion. The differentiator is that peroneal tendonitis pain follows the tendon line and worsens with resisted eversion, while a coalition also shows a rigid hindfoot and a fixed flat foot that tendon irritation alone does not explain.
Juvenile inflammatory arthritis
An inflammatory joint condition affecting the foot can cause stiffness, swelling, and pain that resembles a coalition. The pattern differs: inflammatory arthritis tends to involve more than one joint, can affect both feet and other joints, and often brings morning stiffness and swelling rather than a purely mechanical, activity-linked pain. Blood tests and imaging help separate the two, so a rigid painful foot with systemic features is referred for a rheumatology opinion.
Treating and Preventing Tarsal Coalition
The guiding principle is honest about what podiatry can and cannot do. Conservative care does not dissolve or remould the coalition, it calms the symptoms the coalition produces and offloads the joints that have lost their normal motion. Care is sequenced conservatively first, because many children settle well enough to stay active without an operation, and surgery is reserved for feet that remain painful despite a genuine trial of non-surgical management. Prevention here means preventing symptom flares and repeat sprains rather than preventing the coalition itself, which is already present from birth.
Conservative treatment
These measures are usually combined and adjusted to how much pain the child has and how active they need to be.
- Custom orthoses: a foot orthosis supports the flattened arch and limits the painful motion at the affected joints, which reduces the strain the coalition places on surrounding tissues. Orthoses do not change the coalition, but they are often the mainstay of keeping a child comfortable in daily activity and sport.
- Activity modification: stepping back from the highest-impact running and jumping during a painful flare, then reintroducing load gradually, allows the irritated joints and guarding muscles to settle. The aim is to keep the child moving with low-impact options rather than resting completely.
- Immobilisation during a flare: a short period in a walking boot or cast can rest a foot that is acutely painful or in strong peroneal spasm, breaking the cycle of guarding before rehabilitation resumes.
- Supportive footwear: a shoe with a firm heel counter and adequate midsole stiffness reduces the demand on the restricted joints through long school days and helps the orthosis do its work.
- Physiotherapy and rehabilitation: guided stretching of the tight calf and peroneal muscles, plus strengthening and balance work, help manage spasm and reduce the tendency to sprain. Our physiotherapy service can support this alongside the podiatry plan.
When conservative care isn’t enough
Where pain persists despite orthoses, activity modification, and a fair trial of rehabilitation, the next step is confirmation and a surgical opinion. Plain X-rays can suggest a coalition, but a CT scan best defines a bony bridge and an MRI best shows a cartilaginous or fibrous one, so imaging is arranged to map exactly which joint is involved and how much of it is fused. A referral to an orthopaedic surgeon is appropriate at this point. Surgical options depend on the size and location of the bridge and the state of the surrounding joints, ranging from removing the coalition to fusing the affected joint in more advanced cases. The decision sits with the surgeon, and podiatry continues to support footwear, orthoses, and rehabilitation before and after any procedure.
Have Your Tarsal Coalition Assessed at Straits Podiatry
A rigid, painful flat foot in an older child deserves an accurate diagnosis rather than another round of generic sprain rehab. At Straits Podiatry, an assessment for a suspected tarsal coalition includes a history of the pain and sprains, the tiptoe and hindfoot-motion tests that separate a rigid foot from a flexible one, gait analysis, and a footwear review, with onward referral for CT or MRI where imaging is needed to confirm the bridge.
Where a coalition is confirmed, our podiatrists can care for the symptoms with custom orthoses, activity guidance, and footwear advice, and coordinate rehabilitation with our physiotherapy service, while working alongside an orthopaedic surgeon if an operation is being considered. If your child has a flat foot that will not form an arch on tiptoe and keeps aching or spraining, book a consultation for an assessment at any of our three Singapore clinics.
Frequently Asked Questions About Tarsal Coalition
Will my child grow out of a tarsal coalition?
No. A tarsal coalition is a structural bridge that is present from birth and hardens with growth, so it does not resolve the way a flexible flat foot often does. What can improve is the symptoms. Many children become comfortable enough with orthoses, activity adjustment, and rehabilitation to stay active without surgery. The coalition remains, but a well-managed foot can carry a child through sport and daily life with little trouble. Waiting for it to disappear is not the right plan once pain has appeared.
Does a tarsal coalition always need surgery?
No. A good proportion of children settle with conservative care and never need an operation. Surgery is considered when pain continues despite a genuine trial of orthoses, activity modification, immobilisation during flares, and rehabilitation. The choice of procedure depends on the size and location of the bridge and the condition of the nearby joints, and that decision is made by an orthopaedic surgeon after imaging. Conservative management is almost always the starting point, not surgery.
Can a tarsal coalition be seen on an X-ray?
Sometimes, but not reliably. A calcaneonavicular coalition can show on a plain X-ray taken at the right angle, while a talocalcaneal coalition is often hidden and easy to miss on X-ray alone. A CT scan defines a bony bridge in detail and is the usual choice for surgical planning, and an MRI is better for a cartilaginous or fibrous bridge that has not yet turned to bone. This is why a normal X-ray does not rule out a coalition when the clinical picture fits.
Why does my teenager keep spraining the same ankle?
Repeated sprains on one side, especially with a stiff flat foot, are a recognised sign of a tarsal coalition. Because the fused joints cannot swivel to adapt to uneven ground, the ankle takes the strain and gives way, and the guarding peroneal muscles add to the instability. If ordinary sprain rehabilitation is not holding and the foot will not form an arch on tiptoe, the ankle is worth assessing for an underlying coalition rather than being treated as a simple recurrent sprain.
Can my child still play sport with a tarsal coalition?
Often yes, particularly when symptoms are managed. Many children continue sport with the help of custom orthoses, supportive footwear, sensible load management, and rehabilitation for the calf and peroneal muscles. High-impact running and jumping may need to be dialled back during a painful flare and reintroduced gradually. If pain keeps interrupting play despite these measures, that is the point at which imaging and a surgical opinion are discussed. The aim throughout is to keep your child moving comfortably.
Can orthotics cure a tarsal coalition?
No, and it is important to be clear about this. Orthoses do not remove or remould the bridge between the bones. What they do is support the flattened arch and limit the painful motion at the affected joints, which for many children is enough to control the symptoms and keep them active. They are a management tool, not a cure. A cure, where one is needed, means a surgical procedure decided on by an orthopaedic surgeon.