O-shaped leg can play ball without any harm, pay attention to exercise not too intense can. O-shaped legs, that is, knee inversion, the body weight will be too much concentrated in the inner side of the knee joint joint surface. o-shaped legs can be normal ball games, sports, there is no harm, but should pay attention to sports should not be too intense, the exercise frequency should not be too high, because excessive pressure and friction will lead to wear and tear of cartilage surface of the inner side of the knee joint, which is prone to cause secondary osteoarthritis. The biggest danger of O-shaped legs is that it gradually produces knee pain with age, and it is easy to affect normal walking when you get older. You should pay attention to the posture of walking and sitting, and avoid stilted legs, sitting with legs crossed, and walking in an outward-facing position. O-shaped legs should go to the hospital, under the guidance of the doctor for correction and treatment.