If a 30-year-old young man experiences knee pain when walking down the stairs, it is often due to patellofemoral arthritis. There is a patellofemoral joint between the patella and the femoral trolley of the knee joint, and when inflammation occurs in the patellofemoral joint of the knee due to excessive exercise or chronic injuries, the pain is more pronounced when walking down the stairs. X-rays and nuclear magnetic examination should be carried out to further confirm the diagnosis, which can often show abnormal signals of cartilage damage and symptoms of cartilage softening, and active treatment should be carried out to avoid going up and down the stairs, avoiding excessive exercise and long-distance walking. At the same time, we should take oral nutritional cartilage drugs, such as glucosamine sulfate, glucosamine hydrochloride, bone peptide tablets for treatment, and go to the hospital regularly to review the nuclear magnetic examination of the knee joint to observe the recovery of cartilage damage.