The posterior tibial tendon is a tendon that passes from the muscle in the leg down the inside of the ankle. Its main function is to support the arch of the foot and help control foot function. The muscle is a very powerful force in doing this, as witnessed when the muscle does not work properly with the collapsing of the arch of the foot (see posterior tibial tendon dysfunction). The most common cause of posterior tibial tendonitis is overuse (as in sports activity) or overload (as in obesity).

The symptoms of posterior tibial tendonitis are usually pain and sometimes swelling along the inside of the ankle joint that may extend into the arch of the foot. It is not usually present at rest initially and usually only made worse with activity. The diagnosis is usually made by a physical examination and history Sometimes an ultrasound or MRI can be used to confirm the diagnosis.

The initial treatment of posterior tibial tendonitis is modified rest, such as the avoidance of activities that aggravate the problem. Anti-inflammatory drugs may be helpful. Foot orthotic devices are very helpful as reducing the load that needs to go through the tendon. If the person with the injury is a runner, they should avoid forefoot striking as this increased the load. Heel striking (even temporarily) substantially reduces the load that goes through the tendon. Physical therapy modalities may also be helpful as healing the damaged tissues. If this is not helpful, then a walking brace may be needed to give a tendon a rest. Sometime surgery is needed to debride the fibrous adhesions. If this occurs, 6-8 weeks in a cast is usually needed.