I would be inclined to ease off that type of exercise and give your knee a bit of a rest. When you were diagnosed with Arthritis, did your Dr give you medication for it? If not, it might be a good idea to talk with him/her about it.
Also, is it possible that you may have injured your knee rather than the arthritis flaring? If it bothers you for more than a couple days, PLEASE get it checked by the Dr. Ask him/her what exercises would be best for you and what would be best left alone, too. Sometimes it can be helpful by asking for a referral to a Physiotherapist for their input. That is their area of expertise and will be able to not only tell you what exercises you are best doing, and best avoided, but also SHOW you how to do them properly - SAFELY!
In the meantime, you may still be able to exercise - think of chair exercises! You can get some real good heart-pumping ones even while sitting!
ALSO in the meantime, you might benefit from applying R.I.C.E. to your knee - Rest, Ice, Compression, Elevation!
Edited by: SLIMMERKIWI at: 6/9/2013 (07:00)