The exact time it takes for swelling to go down in a knee caused by trauma depends on the extent of the injury. If it is a simple localized soft tissue injury with tissue fluid exudation, the swelling will gradually decrease and recover in about 2 weeks. If the swelling occurs outside of the knee joint, it is clinically known as prepatellar bursitis, which is characterized by swelling in the front of the patella and a large amount of fluid in the front of the knee, which produces a fluctuating sensation when pressed, and it takes about 2-4 weeks to recover. If a traumatic injury causes damage to the meniscus or ligaments of the knee and swelling occurs, it often takes 6-8 weeks or longer to recover. Patients are advised to brake and elevate the affected limb promptly after the knee swelling occurs and apply ice to the affected area with an ice pack under pressure for 24 hours. If the pain is severe and unbearable, the patient should immediately go to the hospital surgery or orthopedics department for physical examination, imaging and other related examinations to clarify the cause and then deal with it in a timely manner to avoid delaying the condition.