Chronic Knee Swelling

I am 49 years old. I am in the middle of menopause. For the last two years my knees swell up every 6-8 days for about 5-7 days like clockwork. Doesn't seem to matter what I do physically - I can count on them swelling up and going down again. At their worst, they are very restrictive (no gardening, stairs are very difficult). Have been tested for arthritis, celiac, x-rays are normal. At onset of swelling I experience fatigue and depression. On the days when my knees aren't swollen, I feel fine with good mobility. Anyone experience anything similar? I'm getting disillusioned about ever finding a remedy. Thanks.