A note on this column: This article is general medical information, not a description of a service offered at this practice. Dr. Ishiguro's surgical practice is focused on hip and knee conditions — he does not treat or perform surgery for posterior tibial tendon dysfunction or flatfoot deformity. This column is written to help readers understand a common but often-missed condition and know when and how to seek the right specialist, typically a foot and ankle orthopaedic surgeon or podiatrist.
What's actually happening in the foot
The posterior tibial tendon runs from a muscle deep in the calf, behind the inside of the ankle, to attach along the underside of the midfoot. Its job is to support the arch and control the position of the hindfoot with every step. When this tendon becomes inflamed, degenerates, or gradually elongates — a process called posterior tibial tendon dysfunction (PTTD) — it can no longer hold the arch up properly, and the foot progressively flattens and rolls inward. PTTD is the single most common cause of what's called adult-acquired flatfoot deformity, and in recent years the specialist literature has increasingly referred to the broader condition as progressive collapsing foot deformity (PCFD), reflecting the fact that the tendon is usually just the first structure to fail, with supporting ligaments on the inner side of the foot often becoming involved as the deformity advances.
Unlike a childhood flexible flatfoot, which is usually painless and present from a young age, adult-acquired flatfoot typically develops in one foot at a time, in a person whose arch was previously normal, and it is usually accompanied by pain and swelling along the course of the tendon before the visible flattening becomes obvious.
How common it is — and who it affects
PTTD is under-recognized, in part because early symptoms — aching along the inner ankle after standing or walking — are easy to attribute to general foot fatigue, poor footwear, or simple aging. It is estimated to affect several million adults in the United States, and it is disproportionately common in women over 40, with prevalence peaking around the mid-fifties.
What the evidence shows: A community-based screening study mailed a validated foot-health questionnaire to 1,000 women over 40 registered with a single English general practice, then clinically examined those who screened positive. It found a 3.3% prevalence of symptomatic stage I or II PTTD or established adult-acquired flatfoot deformity in this population — and notably, every affected woman identified had gone undiagnosed despite having characteristic, often prolonged symptoms (Kohls-Gatzoulis et al., Foot Ankle Surg, 2009). The authors argued this supports a low threshold for clinical suspicion in this demographic, since the condition responds far better to treatment when caught before the deformity becomes fixed.
Established and reported risk factors
- Age and female sex — most consistently identified group, with prevalence rising through middle age and peaking around 55
- Obesity — repeatedly associated with both onset and severity in the literature
- Hypertension and diabetes — both linked to tendon degeneration, likely through effects on tendon microvascularity
- Prior trauma or steroid exposure — direct injury to the tendon, or corticosteroid injections near it, can weaken the tissue
- Inflammatory arthritis — conditions such as rheumatoid arthritis can accelerate tendon and ligament failure
The four clinical stages
PTTD was first formally staged by Johnson and Strom in 1989 as a three-stage system based on the condition of the tendon, the flexibility of the hindfoot, and whether the deformity was fixed; Myerson later added a fourth stage to account for cases where the deformity progresses far enough to affect the ankle joint itself. This staging matters clinically because it largely determines which treatments are realistic options.
| Stage | Arch / hindfoot | What's happening |
|---|---|---|
| I | Arch preserved | Tendon inflammation (tenosynovitis) or mild degeneration; pain along the tendon but no visible flattening; single-leg heel raise is usually still possible |
| II | Flexible flattening | Arch collapses and hindfoot rolls inward, but the deformity can still be passively corrected; often can't perform a single-leg heel raise; subdivided into IIa (mild) and IIb (with midfoot abduction, the "too many toes" sign viewed from behind) |
| III | Fixed deformity | Hindfoot valgus and forefoot abduction have become rigid; the subtalar joint is often arthritic by this point |
| IV | Ankle involvement | Deformity has progressed to tilt and eventually degenerate the ankle joint itself, typically from attenuation of the deltoid ligament on the inner ankle |
Symptoms and simple clinical tests
Early on, patients typically notice aching or swelling along the inside of the ankle and midfoot that worsens with prolonged standing or walking and improves with rest. As the tendon weakens further, the arch becomes visibly lower, walking may feel less stable, and pain can shift toward the outer side of the ankle as the collapsing hindfoot causes the heel bone to pinch against the fibula. Two simple findings clinicians look for are a positive single-leg heel raise test — inability to rise onto the toes of the affected foot alone, or rising without the heel rotating inward normally — and the "too many toes" sign, in which more toes than expected are visible from behind due to forefoot abduction.
How the diagnosis is made
Diagnosis begins with a history and the physical examination described above, along with palpation of the tendon for tenderness and swelling. Weight-bearing X-rays of the foot are typically obtained first, since they show the degree of arch collapse and alignment under normal load and help exclude arthritis in the affected joints. MRI or ultrasound is often added to assess the tendon itself — its thickness, the presence of tears, and whether nearby ligaments such as the spring ligament are also compromised — information that becomes particularly important when surgery is being considered.
What the evidence says about treatment
Not every case of PTTD requires surgery, and the right approach depends heavily on the stage at diagnosis, how long symptoms have been present, and whether the deformity is still flexible.
Commonly used treatment options
- Activity modification and immobilization — a period in a boot or cast for acute tenosynovitis to let inflammation settle
- Custom or semi-rigid orthotics and ankle-foot bracing — support the arch and reduce load on the tendon, most effective in Stage I and flexible Stage II
- Structured physical therapy — strengthening of the posterior tibial muscle, including eccentric loading, alongside stretching of a tight Achilles tendon (a frequent contributing factor)
- Tendon transfer with osteotomy — for Stage II disease that fails conservative care, most commonly a flexor digitorum longus tendon transfer combined with a bone-realigning procedure such as a medial displacement calcaneal osteotomy or lateral column lengthening
- Hindfoot fusion procedures — reserved for Stage III (fixed deformity, often with arthritis) and Stage IV disease, where the joints are no longer flexible enough for a joint-preserving reconstruction
What the evidence shows: A structured nonoperative protocol combining a custom orthosis with a supervised exercise program was studied prospectively in 47 consecutive patients with Stage I or II PTTD. After a median of 10 physical therapy visits over roughly four months, 83% had a successful subjective and functional outcome and 89% reported satisfaction, with only 11% ultimately requiring surgery (Alvarez et al., Foot Ankle Int, 2006). This is one of the more frequently cited pieces of evidence that a genuine trial of bracing and structured exercise is worthwhile before considering surgery in appropriately early-stage disease — though outcomes are markedly less favorable once the deformity becomes fixed.
A 2025 systematic review and meta-analysis pooling the nonoperative and operative literature reinforced this staged approach while highlighting how thin some of the evidence base still is.
What the evidence shows: The review found that orthotics combined with stretching produced measurable improvement in Foot Function Index scores, with the largest treatment effect seen in patients who added eccentric strengthening exercises to their orthotic wear. On the operative side, pooling data across 15 case series covering several hundred operated feet, the review found consistent, statistically significant improvements in AOFAS hindfoot scores and radiographic alignment measures (calcaneal pitch, talometatarsal and talonavicular coverage angles) after tendon transfer combined with bony realignment procedures — but noted that most included studies were retrospective case series of only low-to-moderate methodological quality, with no high-quality trial directly comparing surgical techniques to guide the choice between them (Adukia et al., J Arthrosc Surg Sports Med, 2025). In practice, this means individual technique selection still depends heavily on surgeon experience and the specific pattern of a patient's deformity, rather than a single evidence-backed "best" operation.
When to see a specialist
Ongoing aching or swelling along the inner ankle that doesn't settle within a few weeks, any visible change in arch height in one foot, or new difficulty rising onto the toes of one foot are all reasonable triggers for evaluation — ideally sooner rather than later, since Stage I and flexible Stage II disease respond far better to bracing and exercise than fixed, later-stage deformity. This is especially relevant for women over 40 with the risk factors above, given how often the condition goes undiagnosed at a stage when nonoperative treatment still has the best chance of working.
References (PubMed / Journal)
Johnson KA, Strom DE. Tibialis posterior tendon dysfunction. Clin Orthop Relat Res. 1989;(239):196-206. PMID: 2912622
Kohls-Gatzoulis J, Woods B, Angel JC, Singh D. The prevalence of symptomatic posterior tibialis tendon dysfunction in women over the age of 40 in England. Foot Ankle Surg. 2009;15(2):75-81. DOI: 10.1016/j.fas.2008.08.003
Alvarez RG, Marini A, Schmitt C, Saltzman CL. Stage I and II posterior tibial tendon dysfunction treated by a structured nonoperative management protocol: an orthosis and exercise program. Foot Ankle Int. 2006;27(1):2-8. DOI: 10.1177/107110070602700102
Adukia V, Trivedi R, Houchen-Wolloff L, Mangwani J, O'Neill S, Divall P, Vaishya R. Non-operative and operative management of posterior tibialis tendon dysfunction – a systematic review and meta-analysis. J Arthrosc Surg Sports Med. 2025;6:3-15. DOI: 10.25259/JASSM_43_2024