What Causes Sudden Loss In Body Balance When Suffering From Arthritis?

On Monday morning I collapsed to the floor. My legs just gave ot. I had general weakness throughout my limbs. I went to the ER. They checked me out for a mini-stoke or stroke. All tests were normal. I have chronic backpain due to arthritis. The ER physician suggested nerve damage. Any other thoughts. My DR told me to get knee x-ray since my knee ached.