There have long been discussions as to whether habitual running leads to osteoarthritis of the knee. Some studies have taken place to prove or disprove whether this is the case or not, using imaging and reported pain and function questionnaires.
The majority of studies state that runners actually have a lower prevalence of knee pain than non-runners. Regular running does not increase the risk of developing knee osteoarthritis, and it may in fact protect against it. Those who are inactive are actually more susceptible to suffering knee osteoarthritis, particularly if they are obese, have poor muscle tone and strength, and have a heavy occupational load.
Long distance running has actually shown to reduce bone bruising in middle-aged runners, and does not result in the progression of existing meniscal tears. Evidence also shows there are direct correlations between increased physical activity and reduced cardiovascular events and mortality.
There is however lacking evidence as to whether those currently suffering knee osteoarthritis should start or continue to run without causing further damage.