Algodystrophy: a common unrecognized cause of chronic knee pain

Thirty-three patients with undiagnosed chronic knee pain had features of autonomic disturbance. Thermography is a useful imaging technique for demonstrating this abnormality. The patients lacked the thermographic symmetry observed in 16 normal controls but this returned with resolution of the pain. Recognized radiological and scintigraphic features of algodystrophy were found. The long duration of symptoms, high proportion of young females and the severity of the associated disability were notable. It is suggested that algodystrophy is a more frequent cause of chronic knee pain than previously recognized. Autonomic abnormalities may be less intense in disease at this site, particularly in young females and may be overlooked. This characteristic of algodystrophy of the knee may contribute to chronicity and subsequent disability.