Every time I've played football with my mates over the past few weeks my knee has become swollen and painful. It sounds as if you're not giving your knee enough time to recover from an injury or that there's damage to the cartilage in the knee.
Footballers are particularly susceptible to knee injuries.
In fact, the knee joint is injured more than any other joint in the body during all types of sport. It needs this because when we walk or run, the knee joint is placed under a great deal of stress. Any violent twisting movements, for example an awkward tackle or turning on the ball, may damage the cartilage or the ligaments that support and keep the knee stable. When this happens during a game, your knee is likely to become swollen and extremely painful forcing you to hobble off the pitch. If you're finding that your knee is locking or giving way too, then a damaged cartilage is the likely problem.