Once the knee is sore and swollen at night, suggesting inflammation within the knee, it is necessary to identify the causes of inflammation, the common causes are the following: first, arthritis, such as gouty arthritis, rheumatoid arthritis, or some other causative factors caused by the joint, such as osteoarthritis. Second, the patellofemoral joint wear, patellofemoral joint due to frequent up and down the stairs, up and down squatting or running, etc., are likely to lead to wear and tear of the patellofemoral joint cartilage, when there is wear and tear will produce a sterile inflammation, feel sore and swollen knees when sleeping. Third, there are some traumatic diseases, such as meniscal tears, cruciate ligament injuries or cysts in the joint, which may cause knee pain and swelling.