Background Inflammation and vascular disease have recently been shown to play a role in the pathogenesis of osteoarthritis (OA). Low dose aspirin is commonly used in the prevention of cardiovascular disease. Its effects have been attributed to a variety of actions, including anti-inflammatory effects and effects on platelet function (both anti-thrombotic and anti-inflammatory) and lipids. However whether it affects human joints has not been studied.
Objectives The aim of this study was to examine whether the use of low dose aspirin affects change in knee cartilage volume over 2 years.
Methods 117 people with symptomatic knee OA underwent magnetic resonance imasging of the knee at baseline and 2 years later. Medial and lateral tibial cartilage volumes were measured using validated methods. Annual absolute change and annual percentage change in cartilage volume were calculated. Information about regular low dose aspirin use was collected at baseline, 6, 12 and 24 months. Participants who reported taking regular low dose aspirin (≤ 150 mg per day) at more than 1 time point were defined as being aspirin users.
Results Twenty six participants reported taking aspirin at more than one visit, with 91 not taking aspirin. At baseline, the only significant difference between the 2 groups was that those taking aspirin were older than those who did not (p = 0.03).
In those taking aspirin, annual change in medial tibial cartilage volume and annual percentage change in cartilage volume was approximately half that seen in those not taking aspirin (-50 vs. -102 mm3 and -2.5% vs. -5.5%, respectively, P=0.04 for both). These differences became more significant after adjusting for age, gender, body mass index, initial cartilage volume and severity of radiographic change in the medial compartment. The annual change in medial tibial cartilage volume was -40 mm3 (95% confidence interval (CI) -83, 1.3) in aspirin users vs. -105 mm3 (95% CI -127, -82) in non-aspirin users (P = 0.009 for difference). The annual percentage change in medial tibial cartilage volume was -2.0% (95% CI -4.6, 0.53) in aspirin users vs. -5.6% (95% CI -6.9, -4.0) in non-aspirin users (P=0.02 for difference). There were no significant differences observed in change in lateral tibial cartilage volume.
Conclusions This study showed that in people with knee OA, the use of low dose aspirin was associated with reduced medial tibial cartilage loss over 2 years. This requires confirmation in a randomised controlled trial. If this hypothesis were proven, aspirin may provide a cost effective disease modifying therapy for OA as it is a cheap medication that is already in common use and known to be well tolerated.
Disclosure of Interest None Declared