Leg bend pain usually refers to pain in the back of the knee. The causes of leg pain in the elderly are mainly related to degenerative joint disease, inflammation, trauma or tumor growth. 1. Knee degeneration: For the elderly, knee degeneration is easy to occur with age, so the elderly leg pain. 2. Inflammation: If inflammation occurs inside the knee joint of the elderly, such as osteoarthritis or localized synovitis on the back side of the knee joint, the stimulation of inflammation will easily and directly trigger the symptom of pain in the bending part of the elderly leg. 3. Trauma: If the knee joint of the elderly is damaged by external impact, such as posterior meniscus injury, it is easy to produce the symptoms of pain in the bending part of the elderly leg, and even accompanied by localized swelling. 4. Tumor growth: If there is tumor growth on the back side of the knee joint of the elderly, such as bone tumor, etc., it is easy to trigger the symptoms of leg pain, and at the same time, it will produce the symptoms of swelling. If the symptoms of leg pain are more serious, you need to go to orthopedics for examination and standardized treatment to prevent further aggravation of pain symptoms in the late stage.