Pain in the front of the knee may be caused by patellar tendon injury, knee synovitis, chondromalacia patella and patellar fracture. 1. Patellar tendon injury: the occurrence of this disease is usually related to trauma, such as ice skating, skiing, etc., and common triggering factors include too much exercise in a single session, lack of warm-up exercises, etc.. In the acute stage, the patient’s knee joint will be painful, so some patients have pain in the front of the knee, and there will be local hematoma, limited activities and other symptoms. 2. Knee synovitis: the cause of this disease is not clear, generally believed to be related to degenerative changes in the knee joint, joint injuries, etc., can be induced by trauma, long-term physical labor, obesity and other factors, resulting in patients with pain in front of the knee, swelling, skin temperature rise and other symptoms. 3. Chondromalacia patellae: Studies have shown that the causes of this disease include anatomical structure abnormalities, long-term wear and tear of joints, joint malnutrition, and multiple injections of drugs into the joints. Common symptoms include knee pain, patellar rim pressure pain, etc., which can be manifested as pain directly in front of the knee. 4. Patellar fracture: direct impact injury to the knee joint will lead to patellar fracture, and in severe cases, comminuted fracture can also occur, the patient will have pain in the front of the knee joint, activity limitation, localized swelling, through the X-ray can confirm the diagnosis, and early treatment can make the fracture heal smoothly. There are many causes of anterior knee pain, and it is necessary to go to the hospital to clarify the cause of the disease.