About a week ago, something happend to my knee while trying to pick something up.My friend told me it might of been my knee locking. 3-4 days after the injury it would be painful to walk or do any movement and my knee was swollen. I applied ice and that help but now (week later) it hurts when i try to go down the stairs. I can walk somewhat easily with no pain but i cant run. And also at times, the back of my knee starts to have a sharp pain and/or knee pain begins while im standing or walking.