Hello and thank you for using Healthcare Magic. Honestly, your account is a bit confusing. Are the doctors who said you have a meniscal tear the same as the ones who told you about the MRI results? In any case, in my opinion, you should stick by the doctor who informed you about what the MRI shows, as is it more likely they are correct. If the MRI did not show a meniscus tear, than I do not see any reason whatsoever for undergoing the surgery. Please see a rheumatologist in order to get the right diagnosis and treatment if it does end up to be arthritis. As for smoking weed, it would be a problem if you had to undergo with surgery as it interfere with anesthesia, but if this is a case of joint inflammation, aka, arthritis, then there is no harm in it. I hope this helps. Wishing you all the best.