The common causes of knee swelling and pain the day after a fall include soft tissue injuries, fractures, ligament injuries and so on. 1. Soft tissue injury: due to the role of violence, resulting in skin and subcutaneous tissue around the knee joint injury, causing swelling and pain in the knee joint. 2. Fracture: trauma can lead to knee fracture, including patella, tibiofibula, femur fracture, if the fracture is not serious, the activities of the knee joint can be unaffected or mildly limited, the injury stimulation can appear in the knee joint swelling, pain. 3. Ligament injury: under the action of violence, ligament injury of knee joint can be caused, including medial and lateral collateral ligaments, anterior and posterior cruciate ligaments, patellar ligaments, etc. Swelling and pain at the same time, you can also feel the knee joint instability. Swelling and pain the day after a knee fall, there are more possible causes, there may also be blood vessels and other tissue damage, if the symptoms continue to be unrelieved, it is recommended to consult a doctor in a timely manner, and follow the doctor’s instructions for treatment.