You do not mention if your son's knee appears to be swollen or is red or is warmer than usual. A single painful joint can occur as a result of juvenile rheumatoid arthritis, rheumatic fever or an infected (septic)arthritis among other causes. Your son must be seen by a doctor.
The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal
advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.