Knee pain after exercise may be related to the accumulation of lactic acid, ligament tissue strain or meniscus injury and other factors. 1. Large accumulation of lactic acid: when you suddenly perform intense exercise, the muscle tissue around the knee will produce a large amount of lactic acid due to the fermentation of glucose, which will indirectly cause knee pain when it stays in the muscle tissue, which is a normal physiological phenomenon, and it can be returned to normal slowly after proper rest. 2. Ligament tissue strain: If the movement is too strenuous in the process of exercise, it is likely to cause ligament tissue overstressed and strained, causing local congestion and edema, and continuous aggravation of knee pain symptoms. 3. Meniscus injury: knee pain after exercise may also be caused by meniscus tissue damage, once the meniscus tissue is damaged, not only local pain, but also accompanied by knee popping, restricted activities. If you have knee pain after exercise, you can take appropriate rest and actively observe the situation. If there is no obvious improvement, you must consult a doctor in time, and have an imaging examination such as magnetic resonance imaging of the knee joint to observe the damage of the tissue and carry out the correct treatment under the guidance of the doctor.