The pain on the inner side of the knee after running may be caused by aseptic inflammation such as goosefoot bursitis and medial femoral tendonitis, or it may be caused by injuries to the medial meniscus, medial ligament and other parts of the knee. 1. Aseptic inflammation: the medial side of the knee joint has soft tissues such as the medial femoral muscle and the goosefoot constituted by the joint tendons of the suture muscle, thin femoral muscle and semitendinosus muscle. Excessive exercise or repeated wear and tear over a long period of time may cause microinjuries in these areas, leading to the emergence of aseptic inflammation such as bursitis of the goosefoot and tendonitis of the medial femoral tendon and the stimulation of the peripheral nerves, which will lead to the symptom of pain in the medial side of the knee after running. 2. Meniscus and ligament injury: there are soft tissue structures such as medial meniscus and medial collateral ligament inside the knee joint. Incorrect focusing point or long-term strain injury during running may cause excessive wear of medial meniscus or injury of medial collateral ligament, which will lead to abnormal impact of joints in the process of movement, and the symptom of pain in inner side of the knee may also appear. There may also be other causes of medial knee pain after running, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.