Knee pain in an 8-year-old boy may be related to over-exercise, growing pains, and knee inflammation. 1. Excessive exercise: knee pain may be caused by the child’s excessive exercise resulting in pain caused by knee joint strain. 2. Growing pains: it may be related to the child’s growth and development, and knee pain may also occur when the growth and development speed is relatively fast. 3. Knee inflammation: Suffering from knee diseases, such as septic arthritis, rheumatoid arthritis in children, etc. will also show symptoms of knee pain. 8-year-old boy knee pain may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor’s treatment.