(See also Overview of Foot Problems.)
The tibialis posterior tendon helps maintain the normal arch of the foot.
Tibialis posterior tendinosis is usually caused by an excessive ongoing strain caused by a problem with the way the ankle moves. Most often, the person has a low arch, and the foot tends to turn outward when walking, often because the person is overweight. Tendon dysfunction may further contribute to flattening of the arch. The tendon may tear completely, sometimes suddenly in a young person.
In tibialis posterior tendinosis, early on people have occasional pain behind the inner ankle. In time, the pain becomes severe, and swelling occurs. Normal standing and walking become more difficult. Standing on the toes is usually painful and may be impossible if the tendon is completely torn. If the tendon tears completely, the foot may suddenly flatten (called arch collapse) and pain may be felt in the sole.
In tibialis posterior tenosynovitis, pain typically occurs suddenly and the tendon may feel thick and swollen as it winds around the bump on the inside of the ankle (medial malleolus).
Doctors can often base the diagnosis on the person’s symptoms and the results of an examination. However, sometimes MRI is necessary to confirm the diagnosis and to see the extent of tendon damage.
For tibialis posterior tendinosis, devices placed in the shoe (orthoses) and ankle braces worn with supportive shoes or boots are usually sufficient. Complete tears are treated surgically so people can function normally again. Surgery is especially important in young active people with tears that develop suddenly.
For tibialis posterior tenosynovitis, rest and nonsteroidal anti-inflammatory drugs (NSAIDs) are used.