You can exclude rigorous physical activity.
Very little information here.
Uhh. Could be infection. A good case of the flu, can start with achy joints.
Inactivity. Laying around can mess up your joints.
There are conditions. Like DJD. Degenerative Joint Disease.
Arthritis.
Rheumatoid arthritis.
General “wear and tear.”
Loss of lubricant. (Glucosamine, and condroiten can help.)
Lyme disease is another. Allergic reactions too
Lupus
In osteo arthritis pain is not necessarily symmetrical but in RA joint pain will generally be on both sides of the body.