Tuberculous and foreign-body granulomatous reactions involving a total knee prosthesis.

This case report describes loosening of a right knee prosthesis and represents the first report of the simultaneous occurrence of 2 granulomatous processes involving a prosthetic joint. Microscopic examination of the tissue revealed areas of foreign-body granulomas and areas of necrotizing granulomas and caseation. Acid-fast bacilli cultures were positive for Mycobacterium tuberculosis. The pathophysiology of implant loosening following an inflammatory reaction to components of prosthetic materials is discussed. Also discussed is the occurrence of infectious complications and rarity of tuberculous infections associated with prosthetic implants.