The posterior tibial tendon is the key dynamic stabiliser of the medial longitudinal arch, passing behind the medial malleolus to insert broadly on the navicular and all tarsal bones except the talus. It is the most important functional tendon for maintaining normal arch height during single-leg heel rise. Progressive posterior tibial tendon dysfunction from degeneration produces the adult-acquired flatfoot deformity — the most common cause of progressive flatfoot in adults. The navicular tuberosity insertion is the most common site of tendon failure.
Dynamic medial arch support; foot inversion and supination during push-off; hindfoot stabilisation
The clinical stages of posterior tibial tendon dysfunction (PTTD) — tenosynovitis (Stage I), flexible deformity (Stage II), rigid deformity (Stage III), and ankle joint involvement (Stage IV) — guide management. The too many toes sign and single-limb heel rise failure are the primary clinical tests. Orthotics with medial arch support arrest Stage I and II progression. Surgical reconstruction for Stage II involves flexor digitorum longus tendon transfer alongside calcaneal osteotomy and spring ligament repair.
Progressive tendon degeneration producing adult-acquired flatfoot, positive too many toes sign, and single heel rise failure, managed with orthotics in early stages and surgical reconstruction for advanced deformity.
