[Retric]

"There are caveats, though, especially for people who have suffered significant knee injury or are overweight."

Sure, in moderation it's a small net gain, but few are the correct weight, without injury, and run in moderation.

Note: Simply being tall can have the same effect as being overweight and shorter. The knee supports 3d volume on a 2d surface so it has scaling issues. There is a significant peak load difference between a 5'2" runner and a 6'2" runner.

Edit: "We know from many long-term studies that running doesn't appear to cause much damage to the knees," vs. "In one study, Swedish researchers found that exercise, including jogging, may even be beneficial." So, at best "if you have a relatively normal knee and you're jogging five to six times a week at a moderate pace, then there's every reason to believe that your joints will remain healthy." Which is hardly the same things as saying running is not harmful.

[pmahoney]

This seems like a decent review:

http://www.jaoa.osteopathic.org/content/106/6/342.full

"Is there a causal relationship between running and osteoarthritis? The current data are based on small studies, and their results are often unclear."

I've previously come across the cited studies by Lane, "at 9-year follow-up, the results were the same; there was no difference in the incidence and progression of knee and hip osteoarthritis in runners and nonrunners", but had not seen Sohn's comparison of college varsity runners and swimmers, "There is no association between moderate longdistance running and the future development of osteoarthritis. Furthermore, the evidence suggests that neither heavy mileage nor the number of years running are contributory to the future development of osteoarthritis."

On the other hand, Schmitt et al found that "Osteoarthritis of the knee joint is rare in former elite marathon runners. The risk of osteoarthritis of the hip joint seems to be higher than in control subjects who do not engage in much sport."

http://www.ncbi.nlm.nih.gov/pubmed/16932832

[Retric]

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2667877/

"The current evidence in persons who participate in elite sports activity, particularly in sporting groups susceptible to joint injury, suggests that these groups are at increased risk for OA as a result of their participation, but it is unclear whether participation in the absence of injury is harmful. "

Weight and other health issues are a massive and hard to control for Confounding variable in most of these studies. Osteoarthritis causes (weight, injury, bone misalignments etc.) are also likely to inhibit running. At the same time running increases the risk of injury.

Note: Most of these studies are also talking about jogging not running as running is shown to cause damage.

However, from your link "Researchers22 found a significantly higher incidence of osteoarthritis in men (aged 20–49 years) who were involved in high levels of physical activity (ie, walking or running more than 20 miles per week). "