One knee pain in children is not necessarily due to leukemia, but can also be caused by other reasons and should be clearly diagnosed through relevant tests. There are many causes of knee pain in children, but the main cause is growing pains. Children with rapid growth and development will have growing pains when they are deficient in calcium, especially pain in the joints of the lower limbs is the most common, and with more activity, they will have leg pain, knee pain, sore legs and other symptoms, and need to have trace element tests to clarify the calcium deficiency. The discomfort can be gradually reduced with proper calcium supplementation and better nutrition. If one knee pain is present, it is not enough to diagnose leukemia. The diagnosis of the disease also requires relevant laboratory tests such as bone marrow aspiration and immunophenotyping. Therefore, if a child has pain in one knee, he or she can go to a regular hospital and have the relevant tests done to clarify the cause of the disease, and after symptomatic treatment, the discomfort can usually be effectively relieved.