I Have Very Bad Rheumatoid Arthritis In My Left Knee

I have very bad rheumatoid arthritis in my left knee (waiting for replacement). I am taking diclofenac sodium ec 50mg (75mg no longer available except in extreme cases?). I also have the gel, but because of the immediate expense (pay first 70% reimbursed later), I have been using voltaren extra strength. Is there an over the counter drug substitution for the pills? I live in Canada