I have had my tibia in my left knee come out of socket twice and the same in the right knee once. When it happens I have my knee bent and I am twisting my upper body to reach for something. The tibia comes out about 1/4". I immediately twist may body back and it will slide back into place. It causes extreme pain when it is happening and is very tender the next week. After that it will be tender just off and on the tenderness is behind my knee and there is also soft tissue swelling. Since it does not bother me often should I see someone about it?