Pain below the medial side of the knee may be caused by physiological reasons such as excessive exercise of the knee joint and environmental stimulation, or it may be caused by pathologic factors such as injury to the medial meniscus and injury to the medial collateral ligament. 1. Physiological reasons: the lower part of the medial knee joint is the attachment point of the goosefoot muscle group composed of semitendinosus muscle, thin femoral muscle and suture muscle tendon, if running, climbing and other physical exercises for a long period of time, it may lead to the occurrence of the bursitis of the goosefoot, which will cause the pain symptom of the lower part of the medial knee joint; when the knee joint is subjected to cold stimulation for a long period of time, the above mentioned symptom may occur due to the local vasoconstriction. 2. Pathological factors: there are soft tissue structures such as medial meniscus and medial collateral ligament in the deep medial part of the knee. Due to trauma or degeneration, excessive wear and tear of the medial meniscus and excessive pulling and stimulation of the medial collateral ligament may occur, resulting in injury to the medial meniscus or tear of the medial collateral ligament, and pain symptoms below the medial side of the knee may also occur. The cause of pain below the medial knee cannot be accurately determined by the symptoms alone, but needs to be combined with the characteristics of the medical history and other test results to make an accurate judgment, and it is recommended to clarify the cause of the disease under the guidance of a doctor and targeted treatment.