Posterior Tibialis Tendon Dysfunction

Posterior tibialis tendon dysfunction (PTTD) is a progressive failure of the tibialis posterior tendon and is the most common cause of acquired flatfoot in adults.

A 2020 international consensus renamed it Progressive Collapsing Foot Deformity (PCFD), because the ligaments and joint capsules fail as well as the tendon. Women over 40 are most at risk, and the diagnosis is often missed in primary care. Conservative care works best before the deformity becomes rigid.

The tibialis posterior tendon passes behind the medial malleolus and inserts mainly into the navicular tuberosity. It is the main dynamic invertor of the hindfoot and dynamic support of the medial longitudinal arch, working with the spring (plantar calcaneonavicular) ligament.

Degeneration (tendinosis rather than inflammation) usually begins in a zone of relative hypovascularity behind and just distal to the medial malleolus. As the tendon elongates, the arch collapses, the hindfoot drifts into valgus and the forefoot abducts. The spring and deltoid ligaments then stretch, and hindfoot arthritis eventually makes the deformity rigid.

Johnson and Strom classification (Stage IV added by Myerson):

• •Stage I: tendinosis without deformity; single heel raise possible but often painful
• •Stage II: flexible flatfoot; cannot perform a single heel raise. IIa without and IIb with forefoot abduction
• •Stage III: rigid deformity with subtalar arthritis
• •Stage IV: valgus tilt of the talus in the ankle from deltoid failure

Risk factors: female sex, increasing age, obesity, hypertension, diabetes, inflammatory arthritis, pre-existing flatfoot, gastrocnemius tightness and corticosteroid injection near the tendon.