To study efficacy and safety of fish oil in treatment of knee osteoarthritis.75 participants had divided into three groups of 25 people to study efficacy results after taking fish oil 1,000 mg and 2,000 mg once a day for 8 weeks. 1,000 mg of fish oil have EPA 400 mg and DHA 200 mg. All participants had complete visual analog scale for measuring knee pain and knee function. They also had measured 100 meters walking velocity and three steps walking time before taking fish oil. Then they had re-measured all parameters again at 8-12 weeks after taking fish oil to compare the results.All parameters had statistically significant better differences in the group of participants who had taken fish oil when compared to the control group. The average score of patient's satisfaction was 9.06 of 10 and also by verbal response of 50 participants; everyone felt good and happy with fish oil. One participant had hematuriafrom silent CA bladder at 10th week but the other 49 participants were safe without any complications from fish oil.Fish oil 1,000-2,000 mg daily supplementation had significant efficacy to improve knee performance and also are safe in mild to moderate stages of knee osteoarthritics patients. However higher dose 2,000 mg of fish oil had not significant higher efficacy than 1,000 mg of fish oil.