Objective: To evaluate the validity of using the conventional anteroposterior (AP) radiograph of the knee in extension to identify joint space narrowing (JSN) at an early stage of osteoarthritis (OA).
Methods: Grading of JSN using a 0-5 score and quantitative measurement of joint space width (JSW) of the medial and lateral compartments of the tibiofemoral joint in AP and fluoroscopically-assisted posteroanterior Lyon schuss (LS) radiographs of 202 patients with knee OA.
Results: Knees without definite JSN (score<2) were twice as common in AP than in LS radiographs (36.1 versus 18.8%). The number of knees showing definite medial JSN was identical in the two views but 4 knees showing a medial OA in the AP view were classified differently in LS radiographs (3 bicompartmental OA and 1 lateral OA). The frequency of lateral JSN was approximately twice as great in the LS view as in the AP view. JSN score was significantly higher (p<0.0001) and JSW significantly smaller (p<0.01) in the LS view than in the AP view. In knees with definite JSN, JSW of the non-narrowed compartment was significantly (p<0.04) larger than that in knees which did not exhibit definite JSN. Medial JSW and lateral JSW were inversely correlated (p<0.0001).
Conclusions: The standing AP radiograph performed poorly in identifying both the location of JSN in subjects with early tibiofemoral OA (especially, lateral OA) and the severity of JSN. The LS radiographs are preferable to standing AP views for the selection of patients for therapeutic trials of a structure- modifying OA drugs.
- knee joint