Will bike riding, Walking and the Gazelle be sufficient to help my arthritic knees?

[curvesarein]

I am a member of Curves also, but the machine for lower body are hurting and painful. Plus I love to be outside to get sunlight for my depression, I am 55 ,soon to be 56. I don't want to injure myself so badly I can't ride my bicycle, that is my passion and I went 5 miles this morning at a slower pace, uphil and downhill and some straight roads. I used to ride 16 miles until Curves.