Swelling above the knee may be caused by physiological reasons such as over-activity of the knee joint and insufficient warm-up, or it may be caused by pathologic factors such as trauma and degeneration of the knee joint. 1. Physiological reasons: above the knee joint, there are mainly quadriceps muscles composed of rectus femoris, intermediate femoris, medial femoris and other muscle groups, as well as soft tissue structures such as tendons in the migratory areas, if you usually do more exercise or don’t warm up sufficiently before exercising, you may cause aseptic inflammation or acute strains of quadriceps tendons, resulting in congestion and edema of the soft tissues, and the symptoms of above-the-knee swelling appear. 2. Pathologic factors (1) Cruciate ligament, collateral ligament and meniscus injury: there are structures such as cruciate ligament, collateral ligament and meniscus inside the knee joint, if the knee joint is subjected to external force, it may cause injury to these soft tissue areas, and swelling above the knee joint such as meniscus injury and ligament tear may also occur. (2) Degenerative lesions of the knee joint: Degenerative lesions of the knee joint may cause degeneration of the cartilage, excessive wear and tear of the infrapatellar cartilage, and swelling above the knee may also occur. Swelling above the knee may also have other causes such as knee tumors and fractures and other diseases, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.