Collagen has for quite a while now been seen as equal to or possibly better than the traditional Glucosamine-Chondroitin combination for joint osteoarthritis (wear and tear). This latest study suggests that is indeed the case, with just a tiny dose (40mg) of undenatured type 2 collagen improving functional outcomes beyond a typical G-C supplement.
However, bear in mind that the entire study was paid for and researched by people affiliated to the manufacturer! This is not to say it's complete rubbish - it's often the only way a company can get a promising product tested in real world conditions. But it's wise to be wary/skeptical of lone studies like this.
Nevertheless Ergolog have bothered to discuss it here.
And you can read the full free paper for yourself here.
One of the biggest caveats I can see, which hasn't been picked up already, is that MMP-3 (matrix metalloproteinase 3 enzyme) and IL-6 (interleukin 6) are elevated by collagen. That's not typically seen as a good thing, usually a sign of inflammation.
However CRP levels fall significantly, which is usually a sign of reduced inflammation. So perhaps the overall outcome is still positive. MRIs of the joint would be a good way to find out if any recovery has occurred, but lamentably that's not been done here (they're expensive!).
If you have joint issues, I'd recommend for now just sticking with a regular cheap collagen product at a fairly high dose. Nevertheless, this may prove promising after more studies have been completed.