Hello, thanks for your query. Most people with arthritis have osteoarthritis, which commonly occurs with age. There’s another type called rheumatoid arthritis (RA), a serious autoimmune disease. Rheumatoid arthritis is an autoimmune disease that attacks the joints. Although it shares some symptoms with osteoarthritis, the type of arthritis that usually occurs in older people due to wear and tear on joints, there are some key differences. Rheumatoid arthritis can attack at any age, can come on rapidly, and may be accompanied by other symptoms, such as fatigue, morning stiffness.Patellar tendinitis can also cause bilateral knee pain. You should visit concerned doctor to evaluate condition and perform some basic lab investigations like CBC and X-ray. You may need to check RA factor in blood. Once diagnosis is reached, it can properly be managed accordingly. Hope it helps. Take Care!