This is a condition that can cause flat foot. The tibialis posterior (TP) muscle starts on the back of your shin bone (tibia), travels down behind the inside of your ankle and ends up as a very strong, large tendon connected to the bones on the instep of your foot. It has an important role in providing mechanical support to your foot, helping it to function when you are walking. It also helps maintain your foot arch.

How is it caused?

Tibialis posterior dysfunction is caused when the tendon around the ankle becomes damaged by gradual wear and tear, or sometimes after an injury. However, there is sometimes no obvious reason why the tendon has become damaged.

What are the symptoms?

These include foot arch pain and gradual flattening of your foot. The pain and swelling may cause your foot to roll inwards, causing a typical flat foot deformity. In more severe cases, this change in foot shape can lead to arthritis in some joints of the foot.

How is it diagnosed?

Tibialis posterior dysfunction is usually diagnosed after a medical examination and discussion of your symptoms, along with X-rays and an MRI scan.

How is it treated?

• Non-operative treatment: this may involve immobilising the foot and ankle in a specially designed boot to rest the painful tendon. Once the problem has improved, the boot can be replaced on a more long term basis with a special insole for your shoe
• If insoles are not suitable, then more rigid custom-made boots or shoes can help, especially for people who are less physically active
• Surgery: you may be offered tibialis posterior tendon reconstruction or flat foot reconstruction surgery

Important: This information is only a guideline to help you understand your treatment and what to expect. Everyone is different and your rehabilitation may be quicker or slower than other people’s. Please contact us for advice if you’re worried about any aspect of your health or recovery.