Strontium ranelate reduces the number of radiological or radioclinical progressors in patients with primary knee osteoarthritis

Objective(s): Strontium ranelate (SrRan) has demonstrated a structure-modifying activity associated with symptoms improvement in patients with knee OA in a large, randomised, placebo-controlled, double-blind phase-III 3-year study. Patients with joint space width narrowing (JSN) of 0.5 mm over 3 years have a higher risk of undergoing any OA-related lower limb surgery (1). Both radiological progression and lack of improvement in symptoms have been considered by the GREES as clinically relevant endpoints (2). The objective of this planned analysis was to describe the efficacy of SrRan on radiological and radioclinical progression.Material and Methods: 1683 patients with symptomatic primary knee OA (ACR criteria) were included and randomly assigned to SrRan 1 g, 2 g or placebo for 3 years. Radiological progressors between baseline and last observation (defined as patients with a JSN≥0.5 mm) and radioclinical progressors (defined as patients with a JSN≥0.5 mm and with a lack of clinical improvement in symptoms (e.g., ≤20% improvement in WOMAC pain subscore) were compared across groups in the ITT using a chi-square test.Results: Radiological progressors between baseline and last observation were significantly less frequent in the SrRan groups than in the placebo group: 22.3% (p<0.001), 25.6% (p=0.012) in the SrRan 1 g and 2 g groups, respectively, compared to the placebo group (33.1%). The RRR (and NNT) compared to placebo were 32.7% (NNT=10) and 22.7% (NNT=14) in the 1 g and 2 g group, respectively. Similar results were observed when considering patients with both significant radiological progression and lack of symptom improvement. Less radioclinical progressors were observed in the SrRan 1 g and 2 g group than in the placebo group (7.7%, p=0.049; 6.5%, p=0.008 vs. 11.6%, respectively). The RRR (and NNT) compared to placebo were 34.0% (NNT=26) and 44.1% (NNT=20) in the 1 g and 2 g group, respectively.Conclusion(s): Strontium ranelate 1 and 2 g/day reduce the number of knee OA patients with a radiological and radioclinical progression. This shows that SrRan could have a positive effect in decreasing lower limb surgery.