The pain in the knee of one leg may be due to inflammation, tumor, or longer weight-bearing time on one leg, etc. It can be treated by medication and surgery. 1. Inflammation: Chronic osteoarthritis, or inflammation of the joints due to gout or rheumatoid arthritis may lead to the above symptoms. In addition, it may also be caused by bacterial infection, such as staphylococcal infection leading to septic infection of the knee joint, which can be treated with oral antibiotics such as cephradine for antibacterial treatment. 2. Tumor: if the synovial membrane of the knee joint has tumor or the bone around the knee joint has tumor, it can also lead to knee pain, and then we should carry out the nuclear magnetic examination of the knee joint for early diagnosis and treatment. 3. Single-leg weight-bearing for a long time: when single-leg weight-bearing, the cartilage, meniscus and synovial membrane on one side of the knee joint can be damaged, or the inner and outer collateral ligaments of the knee joint can be damaged, which can be manifested as pain in the knee joint. At this time, patients should reduce weight-bearing activities, pay attention to keep warm, can take anti-inflammatory analgesic symptomatic treatment, such as oral ibuprofen. If the pain can not be improved, the drug treatment is invalid, it is recommended to go to the local hospital orthopedic clinic, check the magnetic resonance of the knee joint to clarify the cause, if there is a meniscus injury, arthroscopic surgery is needed. The above drugs should be used under the guidance of a doctor, avoid self-medication.