Playing ball and knee pain symptoms, the following common causes: a. Knee cartilage damage, playing ball and other strenuous sports will cause acute or chronic damage to knee cartilage, the patient will have increased joint wear, which induces synovial inflammation, so that the joint appears serious pain symptoms, and can be accompanied by joint effusion, manifested as joint swelling and restricted movement. MRI can be taken to confirm articular cartilage damage and to understand the extent and degree of articular cartilage damage. Second, meniscus injury, young patients can occur when playing ball meniscus injury, mainly related to rotational movements and jumping movements. Once the meniscus is severely torn, joint interlocking symptoms will also occur, so that joint movement is severely limited. MRI can find the site of meniscal injury. Through the above analysis, we can understand the common causes of knee pain when playing ball, and use the appropriate treatment to relieve the symptoms.