Caroline, thanks for the link to that very interesting paper.

The authors make a plausible case that eating undenatured collagen may help people with RA (which is an auto-immune disease with an inflammatory component) through its ability to intact with gut components of the immune system, though the number of subjects in their study is not large. This whole area (the importance of the parts of the immune system found in the gut) is a "hot topic" for immunologists.

I am not convinced that it is relevant to osteoarthritis which is generally thought to be a "wear and tear" injury of joints, without an inflammatory or auto-immune component.