There are several possible causes for knee pain in the elderly: First, osteoarthritis of the knee joint, osteoarthritis of the knee joint can involve the meniscus and the cartilage of the knee joint, with the formation of bone spurs, there can be symptoms of knee pain when going downstairs, early X-ray and CT examination of the knee joint should be performed for early diagnosis. Second, patellofemoral arthritis, when there is damage to the patellofemoral joint cartilage or bone spur formation, can appear when walking downstairs knee pain symptoms, to carry out knee X-ray examination, nuclear magnetic examination, to carry out early diagnosis and treatment. Third, meniscus injury, if there is damage or tear in the posterior horn of the meniscus, it can also cause knee pain when walking downstairs, early MRI of the meniscus should be performed for early diagnosis and early treatment.