Children with fever say foot soreness may be lactic acid accumulation, rheumatic fever, juvenile idiopathic arthritis and other related. 1. Lactic acid accumulation: children with fever, need to consume a lot of physical energy, muscle energy conversion, resulting in the accumulation of lactic acid in the muscle tissue. You will feel sore feet, as well as generalized muscle pain, limb weakness and so on. 2. Rheumatic fever: usually caused by hemolytic streptococcal infection, in the hidden onset of the disease, fever, as well as joint pain in the feet, fatigue, mental weakness and other symptoms. 3. Juvenile idiopathic arthritis: it may be associated with infection, heredity and other reasons, causing inflammation in the ankle joint area, showing symptoms such as foot joint soreness and fever. Children who say their feet are sore when they have a fever may also have other causes. It is recommended to consult a doctor in time, conduct relevant examinations according to the doctor’s instructions, identify the cause with the help of the doctor, and carry out targeted treatment or treatment.