Will taking rosehip help treat arthritis?

Yes, perhaps: A combined danish/german study found 20% or so of patients somewhat improved using a supplement litozin. It seems to have both anti-inflammatory and anti-oxidant properties and contains a fatty acid (gopo) thought to be similar to fish oil. Many of our current drugs come from plants. A rose hip supplement can concentrate and standardize the potential active ingredients.

Questionable: It is never been proven to help arthritis but there may be other health benefits.