Quantitative evaluation of joint space width in femorotibial osteoarthritis: comparison of three radiographic views

Quantitative evaluation of radiographic methods proposed to improve the detection of joint space narrowing (JSN) in femorotibial osteoarthritis (OA).

Thirty-two consecutive patients with knee OA and five normal controls had three different weight-bearing radiographs of the knee: (1) anteroposterior film of both knees in full extension (extended knees), (2) anteroposterior film of one knee in extension while the patient was standing on the homolateral foot (standing on homolateral foot), (3) posteroanterior film of both knees flexed at 30 degrees (schuss view). Joint space was analyzed blind using both an evaluation of JSN with a six-grade scale (JSN score) and an image analyser computer measurement of the mean joint space width (mean JSW). The medial compartment of medial femorotibial OA knees, the lateral compartment of lateral femorotibial OA knees, as well as both compartments of control knees, were measured. Extended knee and schuss views were made 1 year later in 10 patients for the evaluation of sensitivity to change.

The JSN scores +/- S.D. in schuss, standing on the homolateral foot and extended knee views were 2.75 +/- 1.31, 1.95 +/- 1.3 and 1.66 +/- 1.27, respectively. The mean JSW +/- S.D. in schuss, standing on the homolateral foot, and extended knee views were 2.9 +/- 1.9 mm, 3.5 +/- 1.6 mm and 3.8 +/- 1.5 mm, respectively. Changes in JSN scores and mean JSW with schuss view increased with OA severity. In controls, JSW of the medial compartment did not vary in the three views. JSW of the lateral compartment of controls was significantly larger in the schuss view. The change in JSW after 1 year was -0.41 mm (P = 0.02) in the schuss view and -0.17 mm (P > 0.05) in the extended knee view.

The schuss view is suggested as the most accurate method for the evaluation of JSW in femorotibial OA.