The tibialis posterior tendon inserts predominantly onto the medial navicular and serves to support the medial arch of the foot

Aetiology

• Cause usually unclear
• Tibialis posterior tendon dysfunction is the most common cause of acquired flat foot in adults

Risk factors

• Obese middle aged female
• Risk increases with age
• Hypertension
• Diabetes
• Steroid injection
• Seronegative arthropathies
• Idiopathic tendonosis

Pathophysiology

• The tendon is under repeated stress and particularly with degeneration can develop tendonitis, elongation and eventually rupture
• Usually present for years prior to diagnosis
• Elongation or rupture leads to loss of the medial arch with resulting valgus of the heel and flattening of the medial arch of the foot

Clinical features

• Pain and/or swelling posterior to medial malleolus - very specific
• Change in foot shape
• Diminished walking ability/balance