In short
The tibialis posterior tendon runs behind the inner ankle bone and holds up the arch. When it becomes painful, stretched or torn, the arch gradually collapses, the most common cause of a flat foot developing in adult life (progressive collapsing foot deformity). It causes pain and swelling on the inner ankle and difficulty standing on tiptoe. Treated early, a boot, supportive insoles and a tendon-strengthening programme often settle it; later stages may need tendon and ligament reconstruction or fusion.
What is the tibialis posterior tendon?
It runs from the deep calf muscles, behind the inner ankle bone (medial malleolus), to attach mainly to the navicular in the arch. It is the main dynamic support of the arch, working with the spring ligament underneath.
What causes dysfunction?
- Gradual degeneration with age and overload
- Body weight, diabetes, high blood pressure and steroid use
- A pre-existing flat foot or tight calf
- Injury, or an extra bone in the tendon (accessory navicular)
- Inflammatory arthritis
Symptoms
- Pain and swelling behind and below the inner ankle bone, along the tendon
- A gradually flattening arch, and the heel drifting outwards (“too many toes” seen from behind)
- Difficulty standing on tiptoe on the affected leg
- Later, pain on the outer side of the ankle as the heel bone presses against the fibula
Treatment without surgery
Most effective in early stages:
- A walking boot for a few weeks to rest an acutely painful tendon
- Custom insoles or a brace to support the arch and heel
- Physiotherapy, with a progressive tibialis posterior strengthening programme and calf stretches
- Weight management and activity modification
Surgery
Tailored to the stage and flexibility of the foot:
- Tendon debridement and transfer (usually flexor digitorum longus) to replace the failing tendon
- Spring ligament reconstruction
- Heel realignment (calcaneal osteotomy) and other bone realignments
- Calf lengthening
- Fusion of hindfoot joints when the deformity is stiff or arthritic
See also flat foot (pes planus).
Common questions
Why can I not stand on tiptoe on one leg?
The tibialis posterior tendon locks the heel and midfoot so you can rise onto your toes. When it is weak or torn, a single-leg heel raise becomes difficult or impossible, one of the key signs of the condition.
Will it get worse if I leave it?
It can. In early stages the foot is flexible and responds well to non-surgical treatment. If the collapse progresses, the foot can become stiff and arthritic, which needs bigger surgery. Early assessment is worthwhile.
Talk it through with a specialist
Consultations at Spire Liverpool, Salford and the Isle of Man. New patients £250.
Consultant Foot and Ankle Surgeon, MB BCh, PhD, FRCS (Tr&Orth), FRCS (Glasg), SFHEA, FFSTEd. GMC 6074953. Hunterian Professor, Royal College of Surgeons of England.
Page last reviewed 25 October 2026. This information is general and does not replace an assessment.
Prof Mason's published research on this topic
Peer-reviewed papers by Prof Mason and his colleagues. Links open the paper or its PubMed record.
- Heyes G, Swanton E, Vosoughi AR, Mason LW, Molloy AP. Comparative study of spring ligament reconstructions using either hamstring allograft or synthetic ligament augmentation. Foot & Ankle International, 2020.
- Swanton E, Fisher L, Fisher A, Molloy A, Mason LW. An anatomic study of the naviculocuneiform ligament and its possible role maintaining the medial longitudinal arch. Foot & Ankle International, 2019.
- Chapman J, Dalal N, Molloy A, Jenkinson H, Singh A, Sirikonda S, Mason L. Does a 1st metatarsophalangeal fusion in a patient with pes planus improve the pes planus deformity? A retrospective case series. Foot & Ankle International (accepted for publication).
- Heyes G, Vosoughi AR, Weigelt L, Mason LW, Molloy AP. Pes planus deformity and its association with hallux valgus recurrence following Scarf osteotomy. Foot & Ankle International, 2020.