Bisphosphonates have some reported beneficial effects in treating osteoarthritis (OA). This study examined the effects of bisphosphonate use on symptoms and structural progression of knee OA in participants from the NIH Osteoarthritis Initiative cohort.
People with typical OA trial entry criteria (KL2/3, minimum joint space width 2.5-5.0 mm and pain ≥4 on a numeric rating scale) were classified as bisphosphonate users (≥3 of the 5 years; n=55) or non-users (no use in the preceding 5 years or during follow-up; n=268). Annual data over 4 years were analysed using linear mixed modelling and generalised estimating equations.
Bisphosphonate compliance was 85% at year 1, reducing to 76% by year 4. Numeric rating scale pain scores were significantly reduced among bisphosphonate users at years 2 and 3 (year 3, -0.9 vs -2.2, p=0.004), though not year 4, after adjustment for baseline pain and analgesic use. Differences in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and disability scores did not reach statistical significance at any time point. There was a trend to less joint space narrowing in bisphosphonate users over time (year 4, 0.51 vs 0.29 mm; p=0.06).
Significant reduction in numeric rating scale pain was observed in the first 3 years with bisphosphonate use; diminution of effects by year 4 may reflect reduced compliance. Differences in results obtained using numeric rating scale and WOMAC may reflect different constructs measured by these tools. The beneficial trend on structural progression should be considered in terms of the sample size.