Posterior tibial tendonitis happens when there is inflammation or tearing in the posterior tibial tendon. The posterior tibial tendon helps support your foot, holding up the arch, as you walk. Inflammation or injury to this tendon may lead to flat feet, as the tendon is no longer able to support the arch of the foot. The best shoes for posterior tibial tendonitis have a stiff sole that helps give the bottoms of your feet a rest and provide relief from painful symptoms.