Post-tib tendonitis is inflammation of the posterior tibial muscle tendon, a tendon important for providing structure of the arch of the foot. As with any inflammation, there will be pain and swelling. When this tendon is stressed, it’s easy for the arch to collapse. Once the arch support is lost, the feet flatten and pain worsens. The condition can progress to create plantar fascitis and heel spurs. Cause Flat feet may cause post-tib tendonitis, as will overusing the foot muscles which happens when a runner quickly increases the distance he runs. The longer that a person has flat feet, the more prone a person is to develop post-tib tendonitis. Treatment and Prevention Treatment involves altering the over-pronation that is occurring in the foot. This is easily accomplished with proper orthotic arch supports, shoe inserts and possibly heel lifts or heel cups. The purpose of the heel support is to properly line up the bones in the foot so that they don’t over-pronate. Prevention involves an examination of the types of activities you are doing. If contributing to the post-tib tendonitis with overuse, this needs to stop immediately so healing can begin.