Reduced pain from osteoarthritis in hip joint or knee joint during treatment with calcium ascorbate. A randomized, placebo-controlled cross-over trial in general practice

Jensen NH · Ugeskrift for Laeger

The only randomized placebo-controlled trial of vitamin C with an osteoarthritis pain endpoint, and it is positive and small. Intention-to-treat, calcium ascorbate beat placebo on the 100 mm pain scale by a mean 4.6 mm (95% CI 1.2-8.0, p=0.0078), with the Lequesne function index and patient preference following. The author's own reading is in the paper: the effect is less than half what is commonly reported for NSAIDs.

Population

Patients with radiographically verified symptomatic hip and/or knee osteoarthritis, ten general practices in Denmark

Intervention

1 g calcium ascorbate daily for 14 days

Comparator

Identical placebo, crossover with a 7-day washout

Limitations

Fourteen days per arm — far too short for a structural claim, and short even for a symptomatic one. A 4.6 mm difference sits well below the 15-20 mm usually treated as the minimal clinically important difference on a visual analogue scale. Published in Danish with an English abstract; the calcium in calcium ascorbate is an uncontrolled co-intervention. Never replicated in over twenty years.