Posterior tibial tendon dysfunction is not a common sports injury and is more likely to affect older people. Posterior tibial tendon dysfunction is occurring more often in runners. When posterior tibial tendon dysfunction does occur in an athlete it is serious. The cause of posterior tibial tendon dysfunction is generally an issue where the posterior tibial muscle and tendon complex can no longer carry out its function of supporting the arch of the foot. This leads to a progressive flat foot and rearfoot pronation with progressive pain. It is the most common cause of adult acquired flat foot. When posterior tibial tendon dysfunction occurs in an athlete, they really need to stop all weightbearing sports activity immediately and be prepared for up to at least six months before they can return to sport. One of the biggest concerns about posterior tibial tendon dysfunction is that it gets confused with posterior tibial tendonitis and this can lead to unnecessary complications if they are mixed up. The treatment of posterior tibial tendon dysfunction is rigid foot orthotics with motion control shoes. If this does not stop the progression, then surgery is needed.