I was diagnoised as knee ostioarthritis in the begining of it im 39 years im going to gym for aerobic but my knee pain increase after can i continue?

Yes : People with arthritis who exercise have less pain than people who don't. Maintain proper weight - for every 1 lb. A person is over weight, the knee sees 4 lbs. Avoid high impact aerobics. Avoid anything that makes the knee feel worse. Swimming, cycling or spinning, and walking are all good. Ice is your friend. For persistent pain look into synvisc (hylan g-f 20) or similar injections.

Low impact: If you have a loss of cartilage in your knee (arthritis), you still need to exercise for health benefits. Low impact is always favored. This would include swimming, biking, elliptical machine use. Walking is moderate impact but still better than high impact activities such as running or jumping. You could also try treatments including hyaluronic acid or cortisone injections to ease your pain.