EXTENDED REPORTS Correlation between radiographically diagnosed osteophytes and magnetic resonance detected cartilage defects in the patellofemoral joint

Objective—To assess the correlation between radiographically diagnosed osteophytes in the axial and lateral view of the patellofemoral joint (PFJ) and (1) magnetic resonance (MR) detected cartilage defects in the same joint and (2) knee pain. Methods—Fifty seven pepole with chronic knee pain, (aged 41–58 years, mean 50 years) were examined with axial and lateral radiograms when standing of the right and the left PFJ. The presence and grade of osteophytes was assessed. On the same day, a MR examination was performed of the signal knee with proton density and T2 weighted turbo spin-echo sequences in the sagittal and axial view on a 1.0 T imager. Cartilage defects in the PFJ were noted. The subjects were questioned for current knee pain for each knee. Results—Osteophytes at the PFJ had a specificity varying between 59 and 100% and a positive predictive value between 74 and 100% for MR detected cartilage defects. The corresponding values for osteophytes at the lateral aspect of the femoral trochlea were both 100%. In PFJ with narrowing (<5 mm) osteophytes had a sensitivity and a positive predictive value of 90 and 95% respectively for MR detected cartilage defects, while in PFJ with non-narrowing (>5 mm) the corresponding values were 75 and 65% and the specificity was 50%.A correlation (p<0.05) between osteophytes at the inferior pole of the patella and knee pain was found. Conclusions—Osteophytes at the PFJ are associated with MR detected cartilage defects in the same joint. The relation was strong for osteophytes at the lateral femoral trochlea and in the PFJ with narrowing (<5 mm), but weak in the PFJ with non-narrowing (>5 mm). (Ann Rheum Dis 1998;57:395–400) It is only recently osteoarthritis (OA) of the patellofemoral joint (PFJ) has been recognised as an important cause of pain and disability. Assessment of the PFJ in axial radiograms have been found more reproducible than grading of the joint in lateral radiograms. 3 The axial view was found superior to the lateral view to detect progression of patellofemoral OA. It has also been shown, that joint space narrowing (<5 mm) in the axial view of the PFJ has a high Table 1 Minimal joint space (MJS) in the medial and lateral compartments of the PFJ. The measurement interval was 1 mm, except between 4.5 and 5.5 mm where it was 0.5 mm. Percentages shown in parentheses MJS (mm) Medial PFJ Lateral PFJ