The tibialis posterior tendon inserts primarily on the navicular tuberosity with expansions radiating to all tarsal bones and metatarsal bases 2-4, providing the broadest distal attachment of any tendon in the foot. This broad insertion allows the tibialis posterior to support the entire midfoot arch. Adult-acquired flatfoot deformity from tibialis posterior tendon dysfunction (PTTD) is the most common cause of progressive flatfoot in adults over 40.
The primary active support of the medial longitudinal arch; subtalar inversion; foot adduction
PTTD is classified in four stages by the Johnson-Strom-Myerson system. Stage I: tenosynovitis without deformity. Stage II: flexible flatfoot with inability to perform a single-leg heel rise. Stage III: rigid flatfoot with hindfoot arthritis. Stage IV: ankle valgus involvement. Single-leg heel rise failure (the patient cannot raise the heel off the floor on one leg) is the key clinical test for stage II disease. Treatment ascends from orthotics to medializing calcaneal osteotomy to triple arthrodesis with advancing stages.
Staged PTTD from tenosynovitis to rigid flatfoot managed according to Johnson-Strom-Myerson stage from orthotics to triple arthrodesis.
