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.
Knee swelling usually develops when excess fluid builds up inside the capsule and is caused by either: A) Bleeding in the Joint: aka Haemarthrosis. This is normally caused by an injury and the knee swelling comes on rapidly (within minutes). The swelling can be intense making the knee feel very tight. B) An accumulation of Synovial Fluid: aka knee joint effusion or water on the knee.