This is severe sharp pain behind the knee cap. While I am standing, if I shift to stand on my left leg and let the right one hang the pain is severe. As soon as I put my weight back on the right leg the pain stops. It is intermittent. Lasts for a total of about 1week. It is not related to excessive activity. When this happens it lasts for a few days followed by a few days of a feeling like my knee cap is being lifted up like there is swelling behind my knee cap but not visible swelling.