ASSESSING PROGRESSION OF PATELLOFEMORAL OSTEOARTHRITIS - A COMPARISONBETWEEN 2 RADIOGRAPHIC METHODS

Objective-To compare two plain radiographic methods for sensitivity to detect progression of patellofemoral osteoarthritis. Methods-Two sets of paired skyline and lateral knee radiographs from 54 hospital refer red patients (108 knees) with knee osteoarthritis were taken an averag e of 31 months apart (range 12-40). Films were examined separately in random order by a single observer blind to patient identity and time o rder. Minimum joint space was measured by metered caliper; individual features of osteoarthritis were graded 0-3 using an atlas. Results-Int raobserver reproducibility assessed on 40 knees was to within +/-0.5 m m for skyline lateral facet and +/-0.7 mm for medial facet and lateral views. On the lateral view measured joint space decreased in 51% of k nees but increased in 43%, with overall no significant mean group chan ge with time (-0.2 mm, 95% confidence interval, 0.1 to -0.5). By contr ast on the skyline view joint space decreased in at least one facet in 71% of knees, with significant decrease in mean joint space for both lateral facets (-0.4 mm, 95% CI, -0.2 to -0.6) and medial facets (-0.5 mm, 95% CI, -0.1 to -0.8). Conclusions-It is possible to detect signi ficant joint space loss with time on the skyline view that is not appa rent on the lateral view. The skyline view should be the method of cho ice to detect progression of patellofemoral osteoarthritis.