UCSF

Objective

To analyze associations of suprapatellar fat pad (SPFP) hyperintense signal alterations and mass effect with progression of patellofemoral osteoarthritis (OA) and clinical symptoms over 48 months.

Materials and methods

Subjects from the Osteoarthritis Initiative (n = 426; 51.8 ± 3.8 years; 49.8% women) without radiographic tibiofemoral OA underwent 3T-MRI of their right knees and clinical evaluation using the Knee Injury and Osteoarthritis Outcome Score at baseline and at 48 months. Elevated SPFP signal was assessed on intermediate-weighted, fat-saturated turbo spin-echo (TSE) images. Mass effect was defined as a convex posterior contour. Patellofemoral cartilage, bone marrow lesions (BML), and subchondral cysts were assessed using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Associations of SPFP imaging findings with MRI and clinical progression were assessed using general linear models and logistic regressions.

Results

Baseline SPFP signal alterations were found in 51% of the subjects (n = 217), of whom 11% (n = 23) additionally had a mass effect. Progression of cartilage lesions was significantly higher in subjects with signal alteration versus without (adjusted mean increases, 95% CI; patella: 0.29, -0.07 to 0.64 vs -0.04, -0.40 to 0.31; p < 0.001; trochlea: 0.47, 0.16 to 0.77 vs 0.31, 0.01 to 0.61; p = 0.007). BML progression was also more likely in subjects with signal alteration (OR 1.75, 95% CI 1.09 to 2.82; p = 0.021). Mass effect was not associated with joint degeneration and SPFP findings were not associated with clinical worsening (p > 0.18 for all).

Conclusion

Patellofemoral joint degeneration over 48 months was significantly increased in subjects with SPFP signal alteration, suggesting an association between SPFP abnormalities and the progression of patellofemoral OA.