Sore knees can be caused by overwork, knee osteoarthritis and synovitis. 1. Overexertion: If the patient is overworked, such as often performing strenuous exercise, walking with weight for a long time, running, etc., it may lead to the production of lactic acid in the muscle tissues, which will cause stimulation of the muscles in the knee area, and thus the phenomenon of knee soreness may occur. 2. Knee osteoarthritis: Knee osteoarthritis is a generalized inflammatory disease that occurs in the knee joint and the surrounding tissues. Due to the destruction of articular cartilage and the narrowing of the joint space, knee soreness may occur under the stimulation of inflammation. 3. Synovitis: Synovitis is a joint disease in which the synovial membrane is irritated, resulting in an imbalance of secretion and the formation of fluid. As the synovial membrane is stimulated, it will cause the synovial membrane edema, hyperplasia, which may appear the phenomenon of knee soreness. When patients feel sore knees, it is recommended to consult a doctor for a detailed examination to determine the cause of the disease, and then carry out standardized treatment under the guidance of the doctor.