RADIOGRAPHIC ASSESSMENT OF SYMPTOMATIC KNEE OSTEOARTHRITIS IN THE COMMUNITY - DEFINITIONS AND NORMAL JOINT SPACE

Objective - To evaluate radiographic features of osteoarthritis (OA) t o determine which is more closely associated with knee pain and hence might be used as a radiographic definition of OA in the community. To evaluate joint space width in normal subjects. Methods - 452 subjects from a case-control community study of knee pain (294 women, 158 men, mean age 62 years, range 40-80) underwent AP standing and midflexion s kyline radiographs. Joint space width, measured by metered calliper to 0.1 mm, and graded individual features of OA (osteophyte 0-3, narrowi ng 0-3, sclerosis 0-1, cysts 0-1) were assessed in all three compartme nts independently by two observers who were blind to clinical status. Subjects were categorised as having knee pain by a positive response t o both parts of the question ''Have you ever had pain in or around the knee on most days for at least a month? If so, have you experienced a ny pain during the last year?'' Results - Intraobserver reproducibilit y for joint space width measurements was to within +/- 0.4 mm (95% CI for limits of agreement); kappa values for grading were > 0.7. One hun dred and twenty five subjects were without knee pain or osteophyte. In these radiographically normal knees, mean joint space width varied ac cording to sex but did not decrease with age. A definition based on th e presence of osteophyte greater than or equal to grade 1 in any compa rtment was more efficient at predicting pain than definitions based on either measurement or grading of joint space; there was no clear thre shold of joint space loss at which the likelihood of pain substantiall y increased. The presence of osteophyte at the patellofemoral joint (P FJ) was more sensitive but less specific than at the tibiofemoral join t (TFJ); the addition of PFJ assessment improved sensitivity from 38.1 % to 62.3% with a reduction in specificity from 82.7% to 58.7% for the presence of knee pain. Conclusion - Among men and women in the commun ity, osteophyte is the radiographic feature that associates best with knee pain. Radiographic assessment of both TFJ and PFJ should be inclu ded in all community studies. Joint space loss is not a feature of asy mptomatic aging, and there is not a biological cut off for joint space width below which the likelihood of knee pain markedly increases.