When several joints hurt at the same time, the cause is often different from a single injured joint. Common causes include viral illnesses (which can cause temporary aching in many joints), osteoarthritis (wear-related, usually in older adults), and inflammatory forms of arthritis such as rheumatoid arthritis, which typically causes symmetrical joint swelling and morning stiffness lasting more than 30 minutes.
Autoimmune conditions such as lupus, and crystal-related conditions such as gout, can also affect multiple joints. The pattern matters: which joints, whether they are swollen and warm, how long stiffness lasts, and whether there are other symptoms like rash, fever, or fatigue all help a doctor narrow the cause.
See a doctor if multi-joint pain lasts more than a couple of weeks, comes with swelling, redness, or warmth, or is accompanied by fever, weight loss, or rash. Early diagnosis of inflammatory arthritis is important because timely treatment can prevent long-term joint damage. Blood tests and examination are usually needed to identify the cause.