View this study:
:text=NAC%20was%20found%20to%20have,synovial%20inflammation%2C%20and%20reducing%20pain' class='bbc_url' title='External link' rel='nofollow external'>https://www.ncbi.nlm...d reducing pain.
Taken from the results:
"NAC users had a significantly higher incidence of osteoarthritis (adjusted hazard ratio: 1.42, P < .001) than did NAC nonusers. Also, in analyses stratified by age group and sex, all subgroups exhibited a significantly higher incidence of knee osteoarthritis (P < .0001) among NAC users than among NAC nonusers. The use of oral NAC was associated with nearly four-fold increased the risk of knee OA in the young age group."
Yet then it says this:
"NAC was found to have protective effects against oxidative stress in many organs. According to experimental and tissue culture studies, NAC is effective in clearing free-oxygen radicals, slowing the cartilage degradation process, reducing synovial inflammation, and reducing pain."