Knee pain refers to knee joint pain, and the common causes are over-exercise, trauma, osteoarthritis of the knee, goosefoot bursitis, osteosarcoma and so on. 1. Excessive exercise: after strenuous exercise, there may be transient synovial edema in the knee joint, causing knee pain, which is a normal phenomenon, and the pain can be gradually relieved after rest. 2. Trauma: Under the action of external force, the anterior and posterior cruciate ligaments, medial and lateral collateral ligaments, medial and lateral meniscus injuries or fractures of tibiofibula, femur and patella can cause pain. 3. Osteoarthritis of knee joint: due to old age, trauma, obesity and other reasons, degenerative changes in the knee joint, causing cartilage degeneration, osteophytes and so on, resulting in pain in the knee joint. 4. Goosefoot bursitis: caused by trauma, long-distance running, chronic strain, etc., resulting in aseptic inflammation of the synovial membrane of the medial side of the knee joint, thus resulting in medial knee joint pain. 5. Osteosarcoma: mostly seen in adolescents, it is a kind of malignant tumor, the tumor cells erode the surrounding tissues and cause bone destruction, which can cause knee joint pain, swelling and even deformity. The causes of knee pain are many, and may also be related to osteoporosis and other diseases. If the symptoms continue to be unrelieved, it is recommended to consult a doctor in time to clarify the cause of the disease and carry out targeted treatment.