Soreness in the knee joints of both legs may be caused by physiological reasons, or it may be caused by other reasons such as osteoarthritis, meniscus injury, and synovitis of the knee joint. 1. Strenuous exercise: if the legs for a long time to carry out strenuous exercise will lead to local lactic acid accumulation, the patient will appear legs knee joint soreness performance. This is a normal physiological phenomenon, can not be treated, usually patients will be relieved after rest. 2. Osteoarthritis: the cause of osteoarthritis is not clear, considering trauma, obesity, joint instability and other factors. Patients will experience joint pain, limited joint activity, joint enlargement or deformity, if the patient’s knee joint osteoarthritis will be manifested as knee joint pain in both legs. 3. Meniscus injury: Meniscus injury may be caused by joint torsion and long-term weight bearing of the knee. Patients will have symptoms such as joint swelling, joint pain, limited movement, joint popping, etc. Therefore, patients will have soreness in both legs and knee joints. 4. Other: patients with knee synovitis, knee sprain, knee trauma, gout, rheumatoid arthritis, knee tumors can also lead to bilateral knee pain. If it is caused by strenuous exercise in the legs and knees will generally be relieved after rest, if the disease caused by the legs and knees need timely medical treatment, you can choose the appropriate measures under the guidance of the doctor treatment.