[Treatment of algodystrophy of the knee: diagnostic error and misplacement of the peridural catheter].

A fifty-year-old female patient, with a history of reflex sympathetic dystrophy of the left hand and right ankle, complained of pain in her right knee. The skin was slightly oedematous and red, whereas the knee X-ray was quite normal. These findings were thought to be related to another episode of reflex sympathetic dystrophy, and treatment with continuous epidural morphine and lidocaine was prescribed. Catheter insertion was uneventful. However, the lack of pain relief led to the suspicion of femoral neuralgia. Plain X-ray films of the lumbar spine showed the epidural catheter to be passing through the L2-3 foramen. The catheter was removed. The development of fever and major inflammatory signs of the knee revealed gout arthritis. This case stresses the need for careful repeated clinical examination in order to make the right diagnosis. On the other hand, when the expected effect of drugs administered by the epidural route fails to appear, the catheter's position should be promptly checked by X-ray.