Foot drop, mimicking neuritic leprosy induced by a Baker's cyst

A Baker's cyst of the left knee joint induced foot drop insidiously in a male, Hindu, aged 25 years. On clinical suspicion, that this malady was caused by neuritic type of leprosy, he was administered antileprosy drugs for 6 months without any benefit. On exploration a globular cystic mass, containing gelatinous fluid, was seen to be pressing over the left lateral popliteal nerve. Following removal of this mass, which on histology confirmed to be a Baker's cyst, foot drop and associated motor power impairment disappeared. This case thus highlights the importance of an early exploration and histological diagnosis of a suspected case of neuritic leprosy inducing foot drop and progressively deteriorating, inspite of regular antileprosy therapy.