Effect of estrogen replacement therapy on patella cartilage in healthy women.

Patellofemoral osteoarthritis (OA) is a significant cause of morbidity. Epidemiological data suggests that the use of oestrogen replacement therapy (ERT) may protect against tibiofemoral knee OA. However, the effect on patellofemoral OA is unknown. The aim of this study was to test the hypothesis that long term ERT (greater than 5 years) is associated with increased patella cartilage in post menopausal women.We studied 81 women (42 current users (> 5 yrs) of oestrogen replacement therapy and 39 never users). Articular cartilage volumes were determined by post-processing images acquired in the sagittal plane using a T1-weighted fat suppressed magnetic resonance sequence on an independent workstation.There was no difference in the amount of patella cartilage in women on ERT compared to women on no ERT. After adjusting for patella bone size, years since menopause, body mass index, age of menopause and smoking, ERT users had 2.07 +/- 0.76 ml of patella cartilage compared to 1.93 +/- 0.89 ml in non-users (P = 0.24 for difference).This study suggests that use of ERT for more than 5 years does not have a significant effect on patella cartilage, in contrast to the previously described effect on tibial cartilage. The reasons for this are unknown, but may indicate that there are differences in the mechanisms for development of knee OA at these sites.