There are several reasons for knee pain when running: first, patellar tendonitis or quadriceps tendonitis, often due to long-term, extensive exercise or long-distance walking, resulting in inflammation of the patellar tendon and quadriceps tendon, and pain, early examination, and MRI of the knee joint for early diagnosis. Second, patellofemoral arthritis, severe patellofemoral arthritis can lead to damage to the cartilage of the patellofemoral joint, which can lead to painful friction between the cartilage of the knee when running, and early X-ray and MRI of the knee joint should be taken for early diagnosis. Third, meniscal damage, when the meniscus is damaged or torn in the anterior or posterior horn, it can also appear when running with meniscal pressure, resulting in knee pain, to take early MRI of the knee to see the degree of meniscal damage, if necessary, surgery. Fourth, severe osteoarthritis of the knee, osteoarthritis of the knee can involve cartilage and soft tissue, meniscus damage, can appear when running knee pain symptoms, to take early knee x-ray, and MRI to early diagnosis.