A history of sudden pain or an audible snap is the classic presentation, followed by difficulty walking. On examination there is a visible and palpable defect in the tendon (masked by swelling in late presentation) and weakness of plantarflexion. There may be some active plantarflexion due to plantaris, flexor hallucis longus and tibialis posterior function. Simmonds' test is positive - with the patient prone, or kneeling on a chair, squeezing the calf does not produce passive plantarflexion.
Where the clinical findings are circumspect, the diagnosis can be confirmed by ultrasound or magnetic resonance imaging (MRI), although this is seldom required.
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