Correlation of roentgenographic patterns and clinical manifestations of symptomatic idiopathic osteoarthritis of the knee.

A retrospective review of weight-bearing roentgenograms of 2197 knees in 1894 patients with symptomatic idiopathic osteoarthritis (IOA) revealed six different patterns of tibiofemoral deformity. Five of these patterns expand the taxonomic concepts of Ahlback; the sixth, "nonproliferative," was previously undescribed. It was seen exclusively in patients with varus disease and was characterized by a lack of reactive bony changes. Knees with degenerative changes in the medial compartment constituted the majority of cases (63%). The average age of patients was 72 years for those with varus disease, 79 years for those with valgus disease, and 84 years for those with patellofemoral arthritis (PFA). Bilateral involvement was common only in patients with PFA (79%), suggesting a developmental cause for this subset. There was a female predominance in valgus and patellofemoral disease. The authors report here on a classification system of IOA that has been designed and modified to reflect the unique roentgenographic, epidemiologic, and clinical characterization of the six subsets.