The natural course of arthrosis of the knee.

The aim of this study was to describe the course of untreated or conservatively treated arthrosis of the knee joint. Of 265 patients presenting with knee pain who had weightbearing radiographs taken between 1970 and 1973, 132 (33 men and 99 women) responded to and participated in a clinical followup 20 years later using the Hospital for Special Surgery score and new weightbearing radiographs. Arthrosis was defined as an equal to or greater than 50% joint space narrowing. In 75 of 132 knees of Ahlbäck Class 0 (57%) and 20 of 52 knees of Ahlbäck Class I (39%), the classification remained unchanged. The Hospital for Special Surgery score at followup was compared with the Ahlbäck classes in the 1970s for the 110 cases for which surgery was not done. A higher Ahlbäck class at the time of presentation was associated with lower functional score (Hospital for Special Surgery) 20 years later. In addition, in the contralateral knee a reduction of joint space may occur. In the arthrosis group with total joint space reduction or attrition there was a clinical and radiographic deterioration that would merit surgical intervention to avoid unnecessary loss of function. However, in knees with equal to or greater than 50% joint space reduction (Ahlbäck I) and pain, a considerable number (39%) did not deteriorate radiographically during a 20-year period, and 25% remain free of pain. It appears that the long-term prognosis of mild knee arthrosis is not necessarily poor. A substantial number of these patients will not have progression of the arthrosis.