Whats the meaning of trace amount of fluid in my knee joint seen on an mri?

Common finding. Most patients undergoing knee MRI will have a trace amount of fluid in the joint space. This is considered a normal physiologic finding.
Not important. There is a small or trace amount of fluid in most joints to lubricate the articular surface. This fluid helps preserve the cartilage and makes motion smoother. If there is a small or trace amount in the knee, this is probably normal. Excessive fluid around the knee is something to worry about, and you should see your doctor for this.