Soreness and tenderness in the knee and lower leg can be considered a problem of the locomotor system, as well as other systemic organs or systemic diseases. Injuries and strains to the knee joint, such as meniscal and cruciate ligament injuries, as well as strains and inflammatory reactions to the knee joint, local nerves, such as compression and irritation of the sciatic nerve in the lower extremities, and impaired blood circulation in the lower extremities, can all lead to the development of symptoms. Systemic conditions, such as metabolic disorders, such as abnormal thyroid function, and diabetes mellitus, can cause soreness and tenderness in the knee joints and lower legs. Other systemic diseases produce symptoms of fever and generalized toxic limb weakness, as well as certain tuberculosis infections and tumors. There are also symptoms of potassium and calcium deficiency caused by malnutrition. Patients are advised to go to the hospital for timely consultation, as there are more factors involved.