is a medical term that refers to inflammation in the joints. The inflammation often results in pain (medically known as arthralgias). I would recommend that you take your son to see his pediatrician
. He or she can better evaluate the complaints that he is.
To answer your question -- YES -- children can and unfortunately do get arthritis. This is often different than the arthritis that we think of when thinking of adults. This type of arthritis that many people develop in old age is actually osteoarthritis -- a disease of wear and tear on the joints. Children do not get this unless there is a specific injury
or body deformation that causes an abnormality of the joint function.
But there are other causes of joint inflammation (or arthritis) that children can get. For example, autoimmune disease such as rheumatoid arthritis can occur -- in which the body's immune system accidentally attacks the joints. There is a variant of juvenile rheumatoid arthritis -- although often this occurs with significant fevers. There are other causes which should be evaluated because if there is joint inflammation this can cause long term joint damage.
There are other causes (for example "growth pains") that may be responsible. Please discuss this with his pediatrician for more information.