Women lose patella cartilage at a faster rate than men: a 4.5-year cohort study of subjects with knee OA.

Objectives: Patellofemoral knee osteoarthritis (OA) is a common disease, and a significant cause of knee pain, however few data have examined longitudinal change at the patellofemoral joint. The aim of this study was to examine factors affecting change in patella cartilage over a longer time period than previously examined.

Study Design: Longitudinal study of 77 subjects (58% female) with knee OA underwent magnetic resonance imaging (MRI), with a repeat MRI of the same knee obtained approximately 4.5 years later.

Main Outcome Measures: Annual change in patella cartilage volume, and annual percentage change over 4.5 years.

Results: After adjusting for age, gender, BMI and patella bone volume at baseline, cartilage change was observed at the rate of 2.5% (95% confidence interval, 2.0, 3.0) per annum over 4.5 years. Cartilage was lost at a higher rate in women compared to men after accounting for age, BMI or bone volume at baseline (3.3% vs. 1.4%, respectively, p=0.03). Increased patella bone volume was associated with increased patella cartilage loss (p=0.02). No measures of radiographic severity of disease affected change in cartilage volume.

Conclusions: The increased rate of cartilage loss in women may contribute to the increased prevalence of disease, although the underlying mechanism requires further study. Increased patella bone volume was also associated with increased patella cartilage loss. Whether this is due to biomechanical factors will need to be determined.