Quantitative assessment of radiographic normal and osteoarthritic hip joint space.

Radiographic joint space narrowing (JSN) is the hallmark of progression in osteoarthritis (OA). We developed a technique of measuring joint space of the hip by computer analysis of digitally stored pelvic radiographs. The interobserver coefficient of variation was 3.3%. Mean joint space width (MJSW) and joint space surface were more sensitive to change than interbone distance. In a retrospective analysis of 69 OA hips, MJSW decreased 0.43 +/- 0.43 mm per year and was lower in patients with the hypertrophic form of OA. Limitations were due to radiograph quality. This computerized measurement method is applicable to monitor progression of hip OA and appears to be of value in the evaluation of disease-modifying therapies for OA.