The Dutch study included 100 ankle OA patients who received either PRP injections or a placebo (saline solution). Compared with baseline values, the PRP group improved in pain and function by 10 points (from 63 to 73 points) and the placebo group by 11 points (from 64 to 75 points). A total of 13 adverse events were reported in the PRP group and 8 in the placebo group. Most side-effects were mild. The researchers thus concluded that PRP injections should not be recommended as treatment for ankle OA.

As we wrote last month about PRP and knee OA, improvement in pain after PRP injections is most likely due to so-called "context effects", i.e. the placebo effect and/or effects due to natural pain fluctuations. On average, patients tend to begin new treatments when they are in a "bad phase". As pain tends to fluctuate, it is common that patients experience improvements rather than worsening of symptoms (a phenomenon known as "regression to the mean").

The study is published in the highly regarded American journal JAMA and can be accessed here.