Painful flatfoot deformity.

The posterior tibial muscle is the key dynamic support of the medial longitudinal arch of the foot. When it fails--typically in women older than 40 years of age--progressively, the arch slowly collapses, the heel drifts into valgus, the midfoot flattens, and the forefoot gradually abducts and supinates, resulting in painful acquired pes planovalgus abductus et supinatus. Posterior tibial tendon insufficiency (PTTI) is often misdiagnosed as a chronic ankle sprain, osteoarthritis, or collapsed arch as a result of aging or obesity, and it leaves the patient debilitated. Prompt diagnosis prevents frustration for the patient and allows treatment to be started at an earlier, more easily managed stage. The diagnosis of PTTI is largely a clinical one. An increased awareness of the existence of PTTI should serve to help patients with earlier referral and treatment and by limiting the amount of disability.