Does rheumatoid arthritis have to affect both sides, example both knees at same time or can it just affect one side sometimes? thank you. just a question i had about the disease

Both (bilateral): Rheumatoid arthritis affects joints on both sides of the body. That means if the left knee is affected, the right knee will later be affected if it is not already. The disease may start with only a couple of joints affected, in which case it may not be obvious that both sides of the body are affected. Eventually, the disease affects multiple joints (more than 4) and it will be bilateral.