Egypt's second faith is Coptic Christianity. Copts are heirs of an ancient Christian rite. Coptic Christianity was the predominant religion in Egypt until the 10th century when a lot of Christians diverted to Islam. Christianity itself was brought in Egypt by St. Mark in the middle of the first century AD.
Other possible causes of swelling behind the knee include abscesses (infections); tumors of the skin, soft tissue, or bones; bleeding; deep venous thrombosis (blood clot in the deep veins of the legs); or deformity of the joint after a fracture of any of the bones of your knee joint.
Arthritis is the most common cause of gradual knee swelling, often referred to as water on the knee. Arthritis is the wear and tear of the cartilage and bones. It causes the body to produce extra fluid in the knee, which fluctuates in amounts. Other symptoms of arthritis include stiffness and crepitus (noisy knees!).