Knee pain while running is usually caused by pathological factors, such as ligament injury, meniscus injury, degenerative knee osteoarthritis and so on. 1. Ligament injury: If you do not exert yourself properly when running, it may cause injuries to the medial and lateral collateral ligaments and cruciate ligaments of the knee joints, which will show symptoms such as joint pain, swelling and limitation of activities. 2. Meniscus injury: If the intensity of running is too high or the posture is not proper, it may cause knee meniscus injury. When running, the damaged meniscus will be stimulated and knee pain will appear, and in serious cases, sudden weakness of the joints may also occur. 3. Degenerative knee osteoarthritis: due to strain, trauma and other reasons, cartilage degeneration, subchondral bone plate reactive hyperplasia, triggering the whole knee joint pain and stiffness. Frequent friction of the knee joint during running will aggravate joint pain. In addition to the above reasons, chondromalacia patellae, rheumatoid arthritis and other diseases can also lead to knee pain during running. If running pain is difficult to be relieved on its own, it is recommended to consult a doctor in time and follow the doctor’s instructions to treat the cause.