Johnson and Strom stage I posterior tibialis tendon dysfunction presents with pain and swelling but preserved function and no deformity. Diagnosis is clinical. Pathomechanics explains the overloading of the tendon that may be worsened by a tight gastrocnemius, but systemic inflammatory disease may also be responsible for a stage I condition. Medial heel wedged orthoses are effective in most patients. Surgery usually consists of an open/endoscopic tenosynovectomy. In cases of complete tendon rupture, flexor digitorum longus tendon transfer may be considered. Stage I patients with a higher risk of progression—inflammatory conditions, excessive laxity, obese—may benefit from a “prophylactic” medializing calcaneal osteotomy.