TRANSIENT REGIONAL OSTEOPOROSIS PRESENTING AS A SEPTIC ARTHRITIS

A 52 year old man developed a painful swollen left knee. Clinically th ere was an effusion and radiographs showed local osteoporosis. Sepsis was suspected but tests proved negative and the symptoms gradually set tled. During the course of the following year he developed similar pai n migrating from the left foot to the right knee then to the right foo t. Investigations showed a right knee effusion and 'punctate' radiogra phic lucencies in the patellae thought to be erosions. A bone scan dem onstrated increased uptake at all four sites and sepsis was once again suspected. Biopsies and culture proved negative and a computed tomogr aphic scan confirmed that the lucencies were due to focal osteoporosis rather than erosions. This case of transient regional osteoporosis il lustrates two unusual features of this condition which resulted in dia gnostic difficulty with respect to sepsis.