Epidemiology of osteoarthritis of the knee in a rural Japanese population

Abstract

To investigate the prevalence and risk factors of idiopathic osteoarthritis of the knee in a rural Japanese population, we studied 1547 subjects between the ages of 54 and 79 years who participated in the third Matsudai Knee Osteoarthritis Survey. Data were collected by questionnaire, physical examination, and anteroposterior standing radiographs of both knees. Eighty-four individuals with possible secondary osteoarthritis were excluded from the study. Radiographs were graded from 0 to 4 according to a modified Kellgren and Lawrence scale. Osteoarthritis was defined as being present in a knee if radiographic grades of 2 or higher were detected. Measurement of the femorotibial angle reflected the alignment of the lower extremity. The prevalence of radiographic osteoarthritis of the knee increased with age, and was significantly higher in women than in men (29.7% vs. 10.9%, respectively). However, the prevalence of symptomatic knees with radiographic osteoarthritis (grade 2 or higher) was not significantly different between females and males (35.6% vs. 26.5%, respectively). The femorotibial angle increased with the severity of knee osteoarthritis. Almost all of the knees with radiographic osteoarthritis exhibited a varus deformity due to the loss of cartilage in the medial tibiofemoral compartment. The body mass index increased significantly with each higher radiographic grade of knee osteoarthritis in women, but not in men.